There are more factors to how to size 3b's than just making it 3x's the original raise. These factors include: position, what size villain will call worse with, setting up stack sizes so that your hand plays well postflop (it's frequently ahead when money gets in, for example), etc. Prolly getting much more than that into it would be spoon-feeding.

Flop is a very standard bet/fold for value. You are getting him to call a wide range of worse hands by value betting, but when he raises, he either has hands that A) are ahead, B) are WAY ahead or C) play very well against your specific hand in position.