[mvoss]

Ok, so I did some more math. Maybe this is a waste of time but I'd like to make the numbers a bit more comprehensible. I calculated the value of a bet/check in a number of different situations under the assumption that we have 35% pot equity. Value = 0.35*(number of SB opponents put in)-0.65*(number of bets we put in). Some of the situations below are obviously very unlikely, they are just there to add a little bit of completeness. A lot of situations are left out to make this doable.

BET:
1. 0 callers: 5.5 SB In this case the formula above is obviously not applicable.
2. 1 caller: -0.3 SB
3. 2 callers: 0.05 SB
4. 3 callers: 0.4 SB
5. 4 callers: 0.75 SB
6. We get isolation raised: -0.6 SB

CHECK:
7. Noone bets: 0 SB
8. Hero checks and is the only caller: -0.3 SB
9. Hero checks and there is one more caller: 0.05 SB
10. Hero checks and there are two more callers: 0.4 SB
11. Hero checks and there are three more caller: 0.75 SB
12. CR 2 players: 0.1 SB
13. CR 3 players: 0.8 SB
14. CR 4 players: 1.5 SB

The EV of the entire hand, not counting actions on the turn and river, can be estimated from the numbers above and the assumption that our share of the pot is 35% of the 5.5 SB already in the pot i.e. 1.925 SB.

EV = Probability(1)*5.5 SB+P(2)*(-0.3+1.925) SB+………+P(14)*(1.5+1.925) SB

To get back to your assumptions I think that estimating that we will have only one caller 37.5% of the time we bet is too much. I know we don’t have any reads but 5 out of 9 players saw the flop, that isn’t exactly indicative of a tight table. I think this is a really close situation but to me this is what this situation boils down to. At a loose passive table I’d bet and at a more aggressive table I'd check.