If the Bestow Curse spell causes me to do extra damage, does the target’s death trigger the Necromancy wizard’s Grim Harvest feature?

In D&D 5e using a wizard of the School of Necromancy:

If I cast bestow curse on a monster, then kill it with a crossbow, would it trigger the Grim Harvest feature due to the extra 1d8 damage? Does it matter if the monster had 1 HP?

What about if I cast bestow curse, then hit it with magic missile (and kill it with just 1 missile) – would Grim Harvest trigger off the missile or the curse?

What spell will provide the most healing for a Necromancy wizard’s Grim Harvest feature?

The Necromancy wizard’s Grim Harvest feature allows the necromancer to heal themselves an amount of HP equal to 3 times the level of the necromancy spell used to kill a creature, once per turn.

Instantaneous spells would just heal once per casting. Spells with a longer duration could kill one creature per turn for many turns for repeated healing.

Assuming at least one creature dies each turn, what is the maximum amount of healing a necromancer can get from the Grim Harvest feature from a single casting of a necromancy spell?

Would the Life Cleric’s Disciple of Life feature work with the Necromancer Wizard’s Grim Harvest feature?

The Life Domain cleric’s Disciple of Life feature (PHB, p. 60) says:

Also starting at 1st level, your healing spells are more effective. Whenever you use a spell of 1st level or higher to restore hit points to a creature, the creature regains additional hit points equal to 2 + the spell’s level.

The School of Necromancy wizard’s Grim Harvest feature (PHB, p. 118) says:

At 2nd level, you gain the ability to reap life energy from creatures you kill with your spells. Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell’s level, or three times its level if the spell belongs to the School of Necromancy. You don’t gain this benefit for killing constructs or undead.

Would the Life Cleric’s Disciple of Life feature work with the Necromancer Wizard’s Grim Harvest feature?

For instance, if I’m due to get 8 HP from Grim Harvest for killing a mob with a level 4 Spirit Guardians spell, do I get an extra 6 HP thanks to Disciple of Life?

What are the Grim revenge spell’s “wight” stats?

I am trying to figure out how the “wight” works for the grim revenge spell.

The spell states:

The hand of the subject tears itself away from one of his arms, leaving a bloody stump. This trauma deals 6d6 points of damage. Then the hand, animated and floating in the air, begins to attack the subject. The hand attacks as if it were a wight (see the Monster Manual) in terms of its statistics, special attacks, and special qualities, except that it is considered Tiny and gains a +4 bonus to AC and a +4 bonus on attack rolls. The hand can be turned or rebuked as a wight. If the hand is defeated, only a regenerate spell can restore the victim to normal.

Does this wight also need to be adjusted in other ways for the size? Aka does the damage for its slam attack move down two steps?

Do I look at the “improving monsters” information and move down from medium amending Dex and Str scores?