Line with Middle pair and FD

Everything seems fine here. Raising pre is correct. I would have to ask What the standard preflop raise is? If its 3 then going to 6 would be correct in this spot. If the standard raise is 5 then you may need to go to at least 10 maybe more to get players to fold. The common school of thought is to raise 3 or 4 x and add an x for every player who is in.

On the flop a lot of players will bet their draws in your spot. With 4 opponents you are unlikely to get everyone to fold. A check seems fine. Calling 15 into a 55 pot with all of your outs is not wrong. You didn't mention the tendencies of your players. Are they likely to fold to a raise? Are they calling stations that won't fold? I think I would call here.

Turn makes it less likely someone has a 10. BU checks maybe he stabbed the flopped and has given up.

River SB is definitely not checking a 10. Checking your 9 is okay. Seems to me that you are good here and no one is calling with a worse hand. Lets see if BU stabs again.

It looks fine to me. I'd need some pretty specific reads to checkraise this flop with MP, a non-nut flush draw, and a 2-pair draw that could make someone a straight.

Looks good.

Yeah a lot of these players seem pretty sticky so maybe not best to raise here. Yeah when it goes check I think my 9 should be ok unless they have bigger 9 but not much. Call me

Grunch:

It might help if there are any reads on our V's, or the table dynamics, which may be relevant.

PRE - I have no idea what the standard open size is in this game, but opening 5bb's with 98s seems like it would be in the right neighborhood.

FLOP - Pretty favorable board, and with only one opponent behind us, I think I'd like to c-bet here, for a small size, like 5 again. Proceed with caution if we get raised, but not too concerned about c-betting and calling a raise, if one comes.

Not sure why we'd check, but when we do, the 15 bet from BTN seems a bit too large in a five-way pot, and a bit polar. That sort of sizing seems likely to force opponents to only continue with strong TP for value, or a draw to the nuts.

With SB over-calling pre, and now calling next to act, I'd keep my eye on him. Surely he must have some piece of the board, even if BTN is FOS.

TURN - When SB checks on the top-card pairing, I think I'd discount his having trips, at least somewhat. But regardless, it's become an awkward spot for us to stab at the pot when we checked through on the flop. I think we just need to check again, to let BTN barrel, if he wishes.

RIVER - once the turn checks through, I'd think we have the best hand here a lot, and I'd bet the river for value, maybe 1/2 pot, hoping to get looked up by 1P hands lower than our 9's.