If we assume he has a 75 then call. Why would you give him the rest of your stack when he is a favourite rather then seeing the river when the potodds are often in your favour. 

Lead this flop imo.  There's just one straight out there, and you want to make sure you start building a pot against smaller flush draws.

As played...  SB's play seems really strange for having 57.  If he indeed had 57 he should be leading the flop.  And when the flop checks through he absolutely MUST lead the turn.  Not all fishes understand this, so I guess 57 is still possible, but equally possible is a smaller set or even set+smaller fd.  I would shove here and make sure I get it in against all the dominated hands.  If he EVER has anything other than 57 here you're crushing him so bad that it makes up for the times when you run into the straight.

If he does indeed play 57 this way and only has 57 in this spot you can get on the waiting list for his other tables, because he's sure to be a losing player.

This line shouldn't be 75, but then that probably means it's 75 like always. That said, I would feel so utterly gross if I called, a 5 hit, we both checked, and he had 88 that I would jam here. As Jonna said, any time he shows up with a non-75 hand, we crush him so utterly that it makes up for getting it in as a small dog to the straight.

if he thinks a little - there shouldnt be only 75. SB sees that noone lead flop..he could be x/r 88 lower set here. i mean checking second time is kind of really strange for any player on this stakes

i gonna call and if CO pays extra 10$ its great. but i dont see myself folding any river.