Can you make a don't pass bet after the shooter has established a point ?
No, because that would shift the bias to your favor.
If the point is 4 or 10, then your probability of winning
would be
1 - 3 / ( 3+6 ) = 2 / 3.
If the point is 5 or 9, then your probability
of winning would be
1 - 4 / 10 = 0.60.
And if the point is 6 or 8, then your probability
of winning would be
1 - 5 / 11 = 6 / 11
≈ 0.545
If you could make don't pass bets after a point is established
then
everybody would do this and the casino would
quickly go broke.