Well this is rather easy to summarize. Use the actual DnD rules. Stop with the OP or ignorant homebrew.
One leveled spell per turn is a rule for a reason.
Messing with the Action economy and giving extra actions from items or subclasses will obviously lead to stupid unbalanced or broken things.
The fact that this developer seems to like broken gameplay is a huge red flag for me. Broken is broken even if some minority or casual gamers find it fun.
