Question regarding Pact magic with multiclassing and a class specific bonus

I play a 6 bard/ 4 warlock multiclass. My character recently obtained a rhythm makers drum +3, giving a +3 bonus to my bard spells’ DC and rolls.

I am curious if I were to cast a spell I had taken on my warlock list (hold person) with a bard spell slot, would the bonus increase the DC? DnDB added the bonus to all my characters spells (I know that isn’t right) but thought it may be applicable if a spell is on both lists.

Thank you in advance.

Do I get to add my dexterity bonus to my damage rolls with Shadow Blade?

Tonight I brought out my shadow blade and my GM ruled that I didn’t get to add any extra damage to my shadow blade from my dexterity, because spells only do what they say they do, which is fine and I rolled with it.

My contention is that the spell says I should be able to add my dexterity to damage rolls since it is a finesse weapon. Was it the intent of this spell to deal 2d8 or 2d8+dex on a hit?

For those who want to know: my GM let me use my spell casting ability + PB for attack rolls.

Shadow Blade says:

You weave together threads of shadow to create a sword of solidified gloom in your hand. This magic sword lasts until the spell ends. It counts as a simple melee weapon with which you are proficient. It deals 2d8 psychic damage on a hit and has the finesse, light, and thrown properties (range 20/60).

Finesse says :

When making an attack with a finesse weapon, you use your choice of your Strength or Dexterity modifier for the attack and damage rolls. You must use the same modifier for both rolls.

How can I calculate the optimal amount of attack bonus to give up when using Power Attack?

The Power Attack feat lets you sacrifice attack bonus (AB) to increase your damage.

It’s easy to see that you don’t always want to give up the same amount of AB, and that the optimal amount (assuming you’re trying to maximize your expected damage output) depends on multiple factors. Consider the following two degenerate cases where it’s easy to see that the optimal choice differs:

  1. If your opponent’s AC is so much higher than your AB that you will only ever hit them by rolling a natural 20, then you clearly want to sacrifice the maximum possible amount of AB, since it won’t affect your chance to hit at all (5% in any case), and maximizing your Power Attack damage will result in more damage if you do roll the natural 20.
  2. If your foolish DM has granted you the legendary +Graham’s Number Sword of Munchkinry at level 1, then you clearly don’t want to use Power Attack at all (unless you’ll only miss on a natural 1), because your base damage is so high that even a 5% decrease in your chance to hit will utterly dwarf any piddly damage you get from sacrificing your 1 BAB.

In between these silly cases, though, I’m not sure how to determine the best amount of AB to sacrifice when using Power Attack. It’s not even clear to me what information I need to do so, though I think it includes some or all of the following:

  • The attacker’s AB
  • The defender’s AC
  • The attacker’s BAB (because it’s the maximum amount of AB they can subtract)
  • The number of attacks the attacker is making (if they’re making a full attack)
  • The amount of damage the attack(s) will do on hit
  • How much damage the attacker gains per point of sacrificed AB (e.g., 2 points when using a 2-handed weapon instead of 1 point for a 1-handed weapon)
  • Whether the attack could crit, and its crit stats (range/multiplier) if so

Given this sort of info, how can I calculate the amount of AB to sacrifice to Power Attack that maximizes my expected damage output for the round?

A couple notes:

  • I will happily upvote partial solutions (e.g., ones that only apply to a single attack without considering iteratives, or ones that ignore crits for simplicity’s sake)
  • Ignore considerations that require you to know how close to death the defender is. I’m happy with answers that naively maximize the expected value of my damage output against an idealized combat dummy with infinite HP. Accounting for the desire to maximize the probability of dealing lethal damage against low-HP opponents is, I think, too complicated, and beyond the scope of this question.
  • Ignore the Shock Trooper feat for purposes of this question; obviously if you’re giving up AC for damage instead of AB, it’s a risk/reward judgment call, not a case where there’s an objectively optimal value.

Does the off-hand gauntlet of the Guardian Artificer gain the bonus Intelligence modifier?

I’m trying to figure out in D&D 5e if an Artificer, choosing armorer and guardian, can add their intelligence modifier to attack and damage rolls with their off-hand gauntlet.

Each model includes a special weapon. When you attack with that weapon, you can add your Intelligence modifier to the attack and damage rolls.

Thunder Gauntlets

Each of the armor’s gauntlets.

Would the off-hand gauntlet be considered a part of the special weapon mentioned in the first quote to gain the bonus?

Does Mind whip prevent bonus actions if you take away an action?

The text for mind whip states

You psychically lash out at one creature you can see within range. The target must make an Intelligence saving throw. On a failed save, the target takes 3d6 psychic damage, and it can’t take a reaction until the end of its next turn. Moreover, on its next turn, it must choose whether it gets a move, an action, or a bonus action; it gets only one of the three. On a successful save, the target takes half as much damage and suffers none of the spell’s other effects

Meanwhile, the rules state

[…] anything that deprives you of your ability to take actions also prevents you from taking a bonus action.

If the target chooses a bonus action, it technically shouldn’t be able to do so, as it was deprived of its action. Or is this a case of specific beats general?

Healing Word in a Higher Level Slot — is it still a Bonus Action to cast?

If I prepare healing word in a higher level spell slot, is it still a Bonus Action to cast?

Related context

My DM cites Critical Role as evidence that this is probably not the case because in all the hours he’s watched them play their 5e campaign, they have ruled healing word in higher slots as not a Bonus action.

I’ve not watched Critical Role, so I don’t know if this is even the case in the show.

Does Discipline Focus (Insightful Strikes) add the Wisdom bonus to each attack of Flashing Sun’s full-attack action?

Discipline Focus (Insightful Strikes) states the following:

At 4th level, you can add your Wisdom modifier as a bonus on damage rolls whenever you execute a strike from the chosen discipline. At 12th level, you can choose a second discipline to which this ability applies.

and Flashing Sun states the following:

Flashing sun allows you to make an additional melee attack during this round. As part of this maneuver, you take a full attack action and make your normal melee attacks. However, you can make one additional attack this round at your highest attack bonus. All the attacks you make this round, including the extra attack granted by this maneuver, are made with a -2 penalty.

So, the thing is, Flashing Sun includes a full attack in its description, and Insightful Strikes says "damage rolls", in plural. Does this mean that it adds the Wis bonus to each attack’s damage roll, only to the one added by the strike itself, or neither?

Can you break up your Attack action for a bonus action?

You can do it to move:

If you take an action that includes more than one weapon attack, you can break up your movement even further by moving between those attacks. For example, a fighter who can make two attacks with the Extra Attack feature and who has a speed of 25 feet could move 10 feet, make an attack, move 15 feet, and then attack again. (PHB 190)

It would be necessary for the Great Weapon Master feat:

On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action

As a level 17 Fighter, if I can not place a bonus action between attacks, there are two possibilities:

  1. I have to wait until I finished all 4 attacks of the action, to make another attack as a bonus action
  2. the bonus action attack is wasted unless the kill or crit happens on the 4th attack

So can I take a bonus action in the middle of the attacks of an action?

Does the Tentacle of the Deeps get bonus damage from Spirit Shroud?

Does the Fathomless’ Tentacle deal extra damage from the Spirit Shroud spell as it is you doing the attack via the tentacle? If so does the target have to be within 10 feet of both the warlock and the tentacle?

Tentacle of the Deeps: As a bonus action, you create a 10-foot-long tentacle at a point you can see within 60 feet of you. When you create the tentacle, you can make a melee spell attack against one creature within 10 feet of it. On a hit, the target takes ld8 cold damage, and its speed is reduced by 10 feet until the start of your next turn. — Tashas p.72

Spirit Shroud: Until the spell ends, any attack you make deals ld8 extra damage when you hit a creature within 10 feet of you. — Tashas p.108