You are a much better player then me so I am not sure what use i can be off. Not sure about betting that type of flop against 2 opponents. Espically if ones a fishy player. Turn I think was fine. I think he is likely to have a flush but you are having great odds
and are pot commeted (can't spell) to call because you have put in about $6.25 so far and only need another $5 to call. You are getting 3.5 : 1 to call.
I don't think he is ever bluffing here.
I think a fish would be calling with any flush draws.
That's a good last question. I think shoving just is not getting any value out of the hand even with deeper stack unless he's very very loose. I would probably play the same way even with deeper stacks but if opp bet out river or shoved river then you'll have to re-evaluate. Probably foldig if he's passive but maybe make a crying call.
Like I said I probably not as good as you. This is my own personal opinion