[That Foreign Guy]

CO has 18k, he's put 2.4 of that in so has 15.6k back?

Any raise that a normal player will fold to (here I am talking 3x bet as any less offers way too good odds) will mean he puts in another 4.8k so is left with 10.2k on the flop.

He'll then be getting about 2.5-1 on your flop push (pot 15.6k your bet 10.2k) even with just two overcards he has about 25%. If you're committing to pushing any flop he is committing to calling any flop I think. All that raising does is give you a chance to make a mistake by folding to a threebet push or not pushing a scary flop (well and avoiding losing all your chips but the low variance play is to just call)

So it seems fairly clear your choice boils down to push / call / fold.

Is pushing a good idea?

Assuming CEV is all we care about right now and you were exactly 25k at start and he was 18k

EV Push = equity vs CO range * P(call) + 28200*P(fold) [25k+ other people's chips in middle already]

EV Fold = 24,600

Well that was standard I think. Now the tricky bit - filling in the blanks.

I would say his raising range here is top 35% plus maybe a few random favourite hands for bluffing / spits and giggles. Calling range really depends but let's say 77+ AJ+ and KQ.

This is 8.4%

So now we have:

EV Push = 0.40 * 8.4/35 * 43800 + 28200*26.6/35
= 4205 + 21432
= 25637

EV Fold = 24,600

So it's a push rather than a fold based on hand EV. We can tweak the ranges if you'd like, but I think it will usually be a push. I think it's also a push based on non-hand-EV factors like getting people not to mess with your blinds, and the advantage of having a big stack near the bubble.

So, what about calling?

Well now it gets tricky. Let's do some rough math.

13.3% of the time you flop a set and get 15600-2000 payoff when you take all his chips. So that looks good, but will you get all his chips when you do? I don't think you always will, he needs to get something or be persuaded to bluff all his chips off. I don't think it's worth calling for implied odds only.

The other 86.7% of the time you have a lot of questions to answer.
What percentage of flops do you think you will bet and push him off (whether you're ahead or not)?
Is he a good enough player to make an over the top (semi)bluff when you bet into him?
How often will you get called down by a worse hand? a better hand?

5600 in the pot on flop, you need to bet about 3k minimum. If he calls a half pot he has 12k back in a 12k pot on the turn so he's not absolutely committed but you pretty much have to put 12k at risk to fire a second barrel.

I can think of better times to play a flop than with middle pair OOP. Maybe I'm uncreative and missing out on EV but I'd rather take a definitely fairly +EV play now than try for a bigger play later and risk a disaster.

All up, I think this is a push.