Example fish(calling station) limps 1 $ Mp-Bn Iso 5$ (pot7,5$) we are on sb-bb with X X

We 3bet bluff vs iso because we want to collect dead money and keep fish at the table for long.

1)try to choose hands according our Ev(postflop play oop) also

My first candidates are suited broadway that can be for value vs fish and for blockers vs reg. 

2) What size do u preffer . I d like 12 to win 7.5 It has lower FE but can works well cause we need about 40% of folds