This pot wasnt three bet, he limped and I raised ("two bet")
I put him on a draw because no other hand besides A
T
would make any sense to be played in this fashion. If villain had a strong hand he would have done something besides check call the flop and turn since the board is super drawy with straight and flush possibilities. He may have a hand like KT which would match the flop and turn play, but why in the world would he go all in on the river? The flop and turn play combined with the river shove all equate to a missed draw -- either spades or a ten for the straight