Hey I never really played "fixed limit" before, more of a nl player so I don't know if anything I have to say will be of any use to you or help you out any since I am unsure of what you can bet or raise at any given point and what not...But I checked out the 3 hands you played

First one - I think you played this hand fine, it was a fairly decent flop for you with two overs and nut flush draw, raising the guy there is fine I feel (AJ)

Second one - I think the second one is fine as with the call on the straight draw and you didnt re raise him on the turn with second pair and straight draw (since I believe the flush draw was out as well). The call on the river I believe is fine as well (player dependent of course). I probably don't put him on the queen there as well and just a busted draw.

Third one - I don't like the play on this one at all. The raise pre after a limper with the pocket fives is just bloating a pot up preflop (IMO). Why do you c-bet that flop then check the turn? Are you folding to any bet on the turn pretty much dumping the hand? or are you check calling the turn? Then the river re raise I feel there is no need to 4-bet him after he 3-bet you since he is not doing this with any hands that don't beat you (theres two possible straights on the board, 46 or 810). The only thing you really beat here that he could be raising with is bottom set and maybe 2 pair (but that goes into player dependent as well IMO). so you would have been better off just calling him after he re raised you there instead of re raising him back.

Not sure if any of that helps you out, like I said it is a different type of game than NL (which is what I'm used to) so you have to account for some different things, But I do know you can use the same psychology/reads the same between the two or they are fairly similar in a lot of ways.

Good Luck at the tables buddy