Thoughts? Was there a better line I could have taken?

Bet a lot more on the flop, less than a third of the pot makes no sense with any hand and allows random hearts the right price to outdraw you. Flop turn sizing is better but you've then realised your error earlier in not betting large enough and your river bet looks far too strong. I'd go $7.50 flop then $17.50 turn, which'll make the pot a lot larger by the river

Also, this is beginner's questions, 100NL seems a bit beyond beginners

Thanks. Not a beginner but there are leaks I am trying to plug. I have the roll to play 100NL and have been doing.pretty well at that level. Where's the best place to post these hands please?

The most common GTO sizing for hero's range in this situation is likely to be around 30% of pot, but he shouldn't be betting at a high frequency when OOP multiway. I think I prefer a check-raise to a bet, but it probably doesn't make much difference.
If either villain is a fish/station, then betting bigger would make exploitative sense. As played, either check-raise the turn, or bomb it. Hero needs to be getting stacks in somehow. I'm not sure about that river bet, as I would always have check-raised prior to seeing it.

Small Stakes NL. Not to be confused with Small Stakes FR (full ring)

flop is fine, but on the turn you should really be overbetting for max value vs trips. Bet enough to have around pot sized shove on the river, smth like 23-25$

this is because you unblock all the Ax combos that are never folding. Obviously, when you are bluffing this turn, you also need to overbet. Even extremely simplified strat with just one sizing (overbet) with 99, 44, AK and higher flushdraws (in this specific case you want to bluff with higher flushdraws rather than lower, as higher ones block slowplayed AK and AQ that are always just click-calling, normally you should do the opposite) should give you decently balanced range, normal strat would involve multiple betsizings. But 99 and 44 specifically should always be overbetting here, unless you also want some turn x/raises (which I dont).