As I want to come back into playing poker and being a bit rusty I decided to drop down.
I played more aggressively than my normal with like 28/21/2,5.

Hand1. No reads.

I have AA UTG and raise to 4, BB calls.
100BB stacks.

Flop (9): KT2 with a flush draw
BB checks, I bet 7, BB calls.

Turn (23): 5 offsuit
BB checks, I bet 20, BB minCR to 40, I push...

Thoughts?
I am not used to folding AA in 5max, may be I should reconsider it.

Hand2. BB seems to be regular. He rebuys to 100BB, he is tight, but he is a bit too passive postflop from what I've seen. I've stacked him before, when he 3 bet my openning raise with TT, I floped a flush draw and he floped a set, I got my flush on turn and we got it AI. And he changed place to be in position to me after a few rounds of play.

Effective stacks 130BB

Preflop: I raise to 4,5 in SB with QQ, BB calls.

Flop (9): 732 rainbow
I bet 7, BB calls.

Turn (23): 6 o
I bet 18, BB calls

River (59): 8

I check, BB bets AI 100, I?

Could a river bet be better? Do I call a shove if I bet and he shoves?

Hand3
Again a blind battle. BB seems to be a regular too (not the same as in the 2nd hand.). I think he is quite tight, but I haven't seen him going out of line. Ha was folding to my raises very often and wasn't 3betting.

110BB stacks.

Preflop: I raise KK in the SB to 4,5 , BB calls.

Flop (9): J92 rainbow.
I bet 7, BB calls.

Turn (23): 7
I bet 17, BB raises to 34, I call.

River (91): 5
I check, BB bets AI 65, I?

Hand 1, easy shove.
Hand 2, snap call.
Hand 3, snap call.

People recommending something else probably don't grasp how aggressive 28/21 is.
And how bad people are at adjusting and how easily they get frustrated.

i think you're overestimating how perceptive the average 100nl player is. the first two are folds, the last one is the closest and could go either way imo.