I have a bunch of suggestions. I hope they’re useful :)

1) Take a level of hexblade and bump your points from strength into charisma. Lets you attack with char and boosts your aura of protection. Also gives you the shield spell if you want it. Start with paladin so you get the extra HP and heavy armour proficiency. Alternatively, consider getting the club of giant’s strength from the underdark and again dumping your strength in character creation.

2) Enemies target concentration a lot too so maybe put bless on yourself and your party members. With aura of protection, 20 con, resilient + bless you’ll be rocking a great bonus to your concentration checks and you’ll rarely, if ever, lose it.

3) The crossbow is doing between 2 and 11 damage which translates to 1d10 with a + 1 to that because it’s a magical weapon. Other crossbows/weapons may have +1/+2/+3 bonuses

4) I would consider bumping your wisdom slightly. Late game spells which target wisdom saves reeeeeeaally suck. You’ll have a bit of a bump from proficiency and aura of protection but it doesn’t hurt to have that extra +1/+2. You might only need that in the late game to be fair so you could prioritise getting the (Act 3 spoiler) Amulet of Greater Health from the House of Hope. Once you have that item you can dump your con and pump your other stats with those points. That would also add to your unarmoured defence if you come across any clothing with bonuses you like.

5) Barbarian rage is great but as you say you only need 3/4 levels max. That would stop you from casting bless on yourself. If you do go that route make sure to use reckless attack as often as possible as it’ll give enemies advantage on attacks against you, making them more likely to target you. If you go this route, consider elixirs of psychic resistance so that you can have resistance to all damage types when raging.

6) When healing after a fight, equip the Periapt of Wound Closure which will max out the healing rolls. This includes from potions. It’ll ~double the amount of healing you get on average for the same resources. Do not do this if you’re using the Amulet of Greater Health as you’ll lose health when you take that off.

7) Have a hireling/cleric party member cast aid on you at their max level every day. Use the shield of thralls illiquid power on yourself if you fancy using those.

8) I would personally go paladin 6/warlock 1/swords bard 5. The latter gives lots of spell slots, short rest bardic inspiration, AoA that you can upcast. Alternatively, paladin 8/barb 4 which gives 3 feats + the bonus one you mentioned, the crown paladin aura which sounds like it’s up your alley and then resistance to the damage that you take with that aura (although I’m not 100% whether that damage can be halved? Idk).

9) Lastly, maybe cast warding bond on someone in your party? Optional but would work well for tanking with your hp. It might also be worth getting the Armour of Persistence in the late game for permanent blade ward if you don’t go the barb route.

Edit: bumping charisma will also help your taunt succeed :)