$1.5 NLHE 6-Max STT: What's the correct bet sizing here?

We're in a $1.5 6-max SNG. Big Blind is 60/120 and the average stack is around 19BB so we're pretty short stacked.

From the button I(15 BB, effective stack) picked up . I opened to 2.5 BB. The Big Blind(23 BB, 68% VPIP) calls.

Flop : 6BB :

Big Blind checks. With 12.5 BB left, I bet 2.5 BB. Big Blind called.

Turn : 11B :

Big Blind checks. With 10 BB left, I bet 4.2 BB. Big Blind folded.

I feel like I screwed up the bet sizing. I can use some advice.

1. Will it makes more sense if I shoved the Turn as a semi-bluff? I think the opponent will call the flop with any pair, overcards, or T9 / T8 for a straight draw. That's still 55% range. If I shoved, he will call with AA, KK, QQ, JJ, QJ, 33, and possibly Q3s, Q7, J7s, J3s, 73s. So that means Big Blind will fold 90% of the time if I shove at the Big Blind. I still have straight flush draw so I still have equity when it's called.

2. Does the flop bet even make sense? On one side of the coin, <50% pot bet is just wrong. When I made that bet, I'm trying to shoo away people who don't hit the board in any way, but <50% is obviously too small. On the other side of the coin, then what's the right move here? Pot sized bet will leave me with 6.5 BB so may as well shove? But isn't shove a bit too much here? If shoving here doesn't make sense, does it means I check with a flush draw? If I check this, what's the plan here? Check-fold if I don't complete the flush in the turn?

Disclaimer - i dont claim to be profitable 6max sng player.
1) it is unclear how many chips you have and other players as well.
2) on 15bb, it is usally straight away jam, because you dont want to raise fold this hand, you can justify raise folding only in 2 instances that i can come up wjth: they are nits (which doesnt look like a case) or they are jamming only nuts, aka AJ+ ~55+.
3) on the flop you have to decide what sizing to use to have a nice spr on the future streets. So you have to plan if you want to double barrel jam or triple barrel jam (even though you are not gonna do that in this instance, due to lack of fold equity), this is because you want to apply pressure with your entire range.
4) Pretty hard to comment turn sizing as you accomplish absolutely nothing by betting there small. You dont fold pretty much anything of his range apart of Ax and 22 (if he doesnt jam it pre). So overall as played you just check and hope to hit on the river..

Actually i just realized that on the turn spr is under 1 and your bet on the flop wasnt as terrible as i though, howeever im too lazy to edit the post so ill just add alternative lines here. On the turn wtih this spr you either jam or check and try to hit, you jam only if you think you can get folds from made hands like Jx.

Hope this helps and make sure to add other players stacks next time! GOOD LUCK!

I think, betting around half pot on the flop is totally fine. This is probably, what you would do, if you had a good made hand, and then you should also do the same with your draws. Your bet was a little small, but its not a big deal. If he missed completely, stacks were not deep enough for him to go for some advanced out of position float play, so he is going to play very honest here, regardless if you bet 2,5 or 3,0BB.

On the turn I would jam for maximum fold equity. You have at least 15 outs now and possibly even 18, if your K is alive. The other option is to check back and simply hope to get there. Betting half your remaining stack makes no sense. If he has a made hand, he is probably going to jam, and then you have to call it off anyway.

Given the average stack size you must be 4 players left, and then you are not on the bubble yet. If you take the passive route and lose the pot, you will be left with around the starting stack, and it will not be particularly easy to make it in the money. For that reason I prefer to go for the aggressive option and jam it all in with my monster draw.

Personally with 15bb on the btn I would consider jamming this one preflop. Taking the passive line is fine but we are going to have very little fold equity when we cbet alot of flops and get called therefor making turns awkward and putting ourselves in rough spots.

That being said - when we do open here our raise is too big...when we are under 30bb effective a simple min raise will do it - trust me, if they are not folding for 2 that extra .5 wont make them fold either! Plus if your idea behind all this is to get folds so you don't have to play post flop then just jam and maximize fold equity. So yeah - I'd go 2x here preflop. I know .5bb isnt making a ton of difference in a single hand, but it will make a big difference over multiple hands.

The flop isnt a bad one for us, we have one over, a good straight draw and backdoor flush draw. I tend to check these spots back alot - simply because I dont want to get check-raise and blown off my equity - with a flop this good for our hand though - we may just have to call it off/stick it in there if need be. We do decide to bet - I like the sizing - we get called and go to a turn.

The turn brings a second diamond on board further improving our chances of making a stronger holding by the river - after I bet and get called on that flop my opponent should have some piece of it, and again I pick up equity with this turn - so I tend to check this back ALOT. Just not sure if we can get a J to fold here on the turn and I dont think a Q ever folds here. For me the flop bet sizing was spot on and I like it - now with the pot at 11bb and 10bb in our stack if we are to bet here, we need to take advantage of our 1:1 spr and just go all in. We have tons of outs when we get called, we maximize fold equity and this sizing likely folds our everything but a Q and a good Q should be raising us on the flop I think.

The problem when we bet about 5bb into the pot and we get called is not we have 5bb left and the pot is 21bb...so when we stick our last 5bb in there our opponent is getting 5:1 on their money and there is just no possible way they should be folding given those insane odds! Point is stack sizes get pretty awkward when we do not jam turn...even if we bet 2bb on the turn and jam river we should be jamming 8bb into a pot of 15bb giving our opponent 2:1 on their money and a 33% chance to break even on a call. If we do not jam the turn we open ourselves up to getting called down lighter on the river.

So in conclusion - I would consider jamming preflop - when I don't I open to 2bb - cbet flop for 2bb - probably check turn, though i would at least consider jamming turn - evaluate / jam river when checked to