A good formula for 3-bet sizing is to multiply the opponents raise by 3x and make that your 3-bet size. In this case he made it 12. So you should make it 36. If that seems too small for you then you can do 4x the raise which would make it 48. This, of course, is just a guide that I and others use and does not always need to be followed.

Also if there are any other callers of the 3-bet add another multiplier for each player. For example, random guy raises to 14. Two other people call. Using the 3x rule you raise 5x, because of the two other people. Using the rule you make it (5*14) = 70 to go. Hope this helped.

Raised too little in the first hand oop and way too much in the 2nd.

Also, as a personal preference, I tend to avoid situations in LLSNL games where I think I could end up calling/shoving AI with AK PF unless I feel strongly that I am more than flipping with villains range. I want to be at least at 60/40 favorite to consider it, or be getting a good overlay. Reason being is that i would rather keep the PF pot smaller and play post flop where I know my opponents are capable of making huge mistakes. If I whiff with AK for $12 several times in a row, no big deal, it's easily made up for in the times I float/steal/make a hand and value town or save money when I'm crushed by AA/KK. Better ROI going this route IMO. Some might argue otherwise but I think it's less variance than pushing AK really hard PF and I know it's something that's worked better for my game.

Hand 1 is fine. Just bad variance. You win that the majority.

Hand 2? Against such a tight Villian (limped TT UTG, so raise range is what? JJ+, maybe AQs+, and AKo?) I prefer a smaller 3-bet with the intention of thinking HARD about folding to a sizable 4-bet - his range is 18 combos of pairs (6 JJ, 6 QQ, 3 KK, 3 AA) , and I'm not sure if theres many unpaired hands he's raising, nevertheless 4-betting.

I personally prefer a smaller 3-bet considering the villian, say $35 - $40. If he snap shoves, I narrow his range to QQ+, AKs being liberal, KK+ being conservative.

Against certain villains I find a fold there (too nitty?). Most of the nits I play with may either call or fold PF w/ AK.

As played? Fine. Once your raised to $75, I can't find a fold for those odds, especially not suited.

Both are fine. 3bet folding ak for 75bb is beyond absurd.

Yeah I was wrong about folding AKs in the second hand. I thought he had $300 and misread. He actually has $150 left which means you have to call.

This
In LLSNL, don't 3bet AK OOP unless you know villains range very well and will be comfy getting allin preflop.

IMO AK allin preflop in LLSNL is usually a move made as spew because people like to mentally avoid the tough post flop play and just "get it over with".
( OP I'm not suggesting that you play that way)

With AK in position, 3bet more often and with a smaller size as earlier mentioned. Your ideal conditions for AK are heads up, in position, with initiative.

Very helpful! Thank you very much!

Lesson learned.

This makes so much sense for cash games... Coming from a tournament background, I think I have this problem of over-aggression/pushing coin flips sometimes. Definitely not worth it in cash games. It's better to be conservative with coin flips, and invest when we have the edge. Thanks very much for the comment!

No worries - I take criticism well. That's why I am here