Hand analysis: Turn donk bet with some blocker effects

Played a really interesting hand last night and wanted feedback. Pretty sure I played it close to GTO but curious what you guys think.

1/2 live. I have about $220 because bankroll management

Villain is a younger guy with headphones, probably studies charts and stuff

I open limp UTG with K9o because I like to balance my limping range to be able to be sneaky and limp raise with aces and kings (they'll never suspect I limp with aces because I show up with a lot of garbage like this). He raises to $12. 2 callers. I call because pot odds and implied odds

Flop comes: A 7 4 rainbow

I check. He c-bets $20. 2 fish fold

Now here’s where it gets interesting. I tanked because I put him exactly on AK here. He would raise pre with AK and c-bet this board. Idk, it just made sense. I call because I block the king, which reduces his combos of AK slightly. That’s what pros call "blocker effect"

Turn is a 9

I decide to donk bet $40 to see where I’m at. This is a range merge spot. If he has AK, he probably raises. If he has air, he folds. Either way I gain information.

He calls pretty quickly which confused me. Maybe he randomized and called with AK. Could be AQ sometimes but I discounted that because he didn’t seem confident. When people have real premium hands they seem confident but also kind of tense

River is a 2.

At this point I have second pair with strong removal properties. I thought about jamming for a polarized value bet but decided to check because I wanted to induce a polarized bluff from villain. Then he bets $75

Now I know he can’t have a set because he would’ve raised turn to protect his range. So this felt like AK going for thin value or maybe a missed bluff

Given the pot odds and the blocker dynamics, I tank for 1 minute (to not give any timing tells for the times I wanna tank raise, this is GTO minimum for river decisions) and hero call

He shows 74o for flopped twopair

Honestly I think I played it well. The theory was making sense. Sometimes they just show up with the top of their range

Let me know if my donk bet sizing should be bigger for range protection next time