Is this homebrewed shield weapon balanced?


Relatively new player here who likes to theorycraft. Currently playing a homebrew campaign, and I’m thinking of making a backup character for if my current one (a Ranger, who AFAIK are known to be squishy) dies. My DM is fairly lenient, and I want to make a custom weapon for this character. I like the idea of a gung-ho sword and board Battlemaster Fighter, who excels at crowd controlling large groups of enemies (planning on going Vuman and taking Mobile). The intention is to give the character more options when going sword and board, having the versatility to use Maneuvers at melee or at range by using the Throwing Shield (see below).

Throwing Shield
melee weapon (martial, shield)
AC: +2
Category: Items
Damage: 1d6
Damage Type: Bludgeoning
Item Rarity: Standard
Properties: Range, Thrown, Special, Light
Range: 20/60
Weight: 6 lbs.

Special: Auto unequips (doffs) when used as a thrown attack as part of the Attack action. When used as a thrown attack, the shield immediately returns to the user if the last target it hit is within 60ft of the user. Auto re-equips (dons) when it returns this way. Also gives the user bonus AC when equipped. Manually donning or doffing this shield requires one Action.

Some points I need to make:

  • Usually, standard sword and board using any weapon is legal because a shield isn’t counted as a weapon, it’s a shield, therefore there’s no requirement that the weapon you hold in the other hand needs to be a Light weapon.
  • However, in this case, RAW, since it’s counted as a weapon, the other weapon that you hold in the other hand needs to have a Light property for you to attack with that weapon and the Throwing Shield on the same turn.
  • Basically it means that using the Throwing Shield as a weapon (be it ranged or melee) follows the basic rule of two weapon fighting (not the fighting style).
  • So, it can’t be used as a weapon as long as you’re attacking using a weapon without the Light property with the other hand.
  • Not viable for the Dueling fighting style when going sword and board.
  • Following that, you can still use it as a shield (i.e. granted the bonus AC when equipped) even when you’re not using a Light weapon on the other hand.
  • Manually donning and doffing this shield still requires one Action. Unless a feat overrides this rule (such as Dual Wielder feat).
  • A rare (+1), very rare (+2), and legendary (+3) magic version of this shield exists, the bonus applies to AC, attack rolls, and damage made by this weapon.
  • Variant: 1d8 damage but doesn’t have the Light property. Can go Captain America style. Couples well with the Dual Wielder feat.

For simplicity’s sake, think of it as a weapon that gives bonus AC, instead of a shield. I actually have a few questions, for both the standard and the variant Throwing Shield, but for the purpose of making it less convoluted, I’ll just boil it down to these:
Is this balanced? Are there any weird interactions with feats I’m not aware of?

Bonus question: does lacking the Dueling fighting style makes the sword and board build (specifically this one) considerably less viable?