Hexadin ASI Crossroad

Essentially I'm playing a hexadin and have been making sacrifices to make this MAD character work, but I sometimes can't wrap my mind around where/when to make them. Queue my current dilemma. I'm about to hit level 8 in Paladin, our party just made several thousand gold, and I'm obviously looking to see a bump in power, and there are a couple options I can't make my mind up about. Some additional context: It's a rather combat heavy campaign so these decisions feel even more important.

Option A. Put my ASI into STR so that I can wear plate and push my AC to 20. Tried finessing Mithral plate but I think the DM said 'no' for now, so I shouldn’t count on it.

Option B. Put the ASI into CHA to maximize my spell DC, my to-hit bonus, and Aura of Protection. To me this seems the obvious choice at first as it buffs so many of my classes' core mechanics, but my concern is that doing so will delay the AC increase too long. Level 12 seems like a long time to wait, but maybe that's my lack of experience with these character levels showing.

Stats and party comp:
- Level 7 Conquest Paladin + 1 Level Hexblade Warlock.
- STR 13, DEX 10, CON 17, WIS 10, CHA 18
- Currently have Mitral chain-mail and using sword/board style fighting.
- Other party members are a Monster Hunter ranger, Zealot barb, Genie warlock, Moon druid, and Thief rouge.

I'd love to hear what you would do in my shoes or just what your take on the "best" option would be!