How does AC 30 at level 12 stack up vs Monster Attack Bonuses [closed]

So this is a build I have been working on for few days after a player stated that AC is incredibly difficult to increase and doesn’t feel useful considering the base costs.

Level 2 fighter/10 Wizard

Base Armor:

Plate +18 AC Shield +2

Class abilities:

Fighter: Fight Style Defense +1 AC

Activated abilities:

Wizard: War Magic School Durable Magic +2 AC while holding Concentration Active Concentration spell; Haste (targets include caster) +2AC

Shield used as a reaction when targeted +5AC

Total AC before first turn 21 Total AC after first turn 25 Total AC on reaction after being attacked 30

Two Questions: One How would that stack up against the mid to late game monsters and is there a way to increase the characters AC even further without magical arms and armor?

Bonus questions: When a player grabs say a ring of protection+2 and bracers of Armor +2 do they stack?

Finding Enchanted shields and Plate armor would their magical bonus stack with the bonuses already received from the ring and or bracers?

This caster has the opportunity to use action surge along with haste, could that character cast three 1 actions spells in a single turn. From what I have read the answer would be yes. Haste doesn’t say that you can’t cast a spell as a part of your extra action.