[BotOnTilt]

I would also have checked flop. I've found that betting air into a station is spew. They are both passive, so they might both flat call and you'd find out nothing.

I'd check/call a reasonable bet at the river. IMO if someone flopped top pair they usually don't fold even when you represent the turned scare card. Don't call river. People who raise-bluff the aggressor usually aren't bluffing, and if they do bluff you'll find it out very quickly since they get called so often and you'll be able to make a note then.

I have no idea what the button might have had. Hand reading is a bit hard at NL5. I think the most useful thing to do is watch what your opponents play and how they play it, then you'll be able to make much better guesses on their hands. Also pay attention which villains get stacked with middle pair, TPNK etc so that you know to value bet as much as possible.

Also my usual opening raise at NL5 is 5xBB, I found it to effectively weed out random hands and the pot grows quicker. Not saying that 4BB is bad, just pointing out that it worked well for me.