Poker how should I extract the ,most out of this hand...?

Cut off 9 10 o I raise 3.5 to steal, no limper's this is cash game button calls flop 994 I never seen this guy play he hasn't seen me play either since I hit a monster the board is rainbow I check he bets half pot I call, turn is 10s(9s on board) I check he checks behind river is a complete blank I bet 2/3 of pot he (obv) folds... Only thing he cud beat was a ridiculous thin value bet or a smart float... What did I do wrong?...