What is the appropriate amount of action here?

[yourface]

I dunno, if he's raising J6s preflop in that spot I am probably wrong. we need to be ahead 2/3 of the time to 3bet I believe since we are going to be capped by the straight only. based on your read I think his raising range is [tptk, 6, overpair]

edit: does the 2/3 rule apply when we have such good equity versus the straight? I think we can get away with being behind more often.

ahead of:
99*6, TT*6, JJ*6, QQ*6, KK*6, AA*6, A8*12 = 48

behind:
J6s*4, Q6s*4, K6s*4, A6*16, 66*6 = 34

so we are ahead 58% of the time, which isn't enough

if the only 6s he can have are 66 and A6 it is dead on 66.66%, but that is assuming he always raises with TPTK and overpair on such a scray board.