The general advice is to not post but wait for the blinds to come around to you. However at a full ring table posting from CO is not terrible, because you get to see 6 hands
for the price of 1BB, and while you miss the best seat (BTN), you also avoid the two worst seats (SB and BB). So I am actually ok with this as a way to not waste to much time waiting for blinds to come around. But for obvious reasons we should not post UTG, as this opponent did, and I would also never post in a 6-max game.
No reason to raise junk, and if someone else raise, just fold. But they gave you a free look at the flop, which is great.
Obviously a great flop, since you flopped top and bottom, and while its not the nuts, you are very likely to have the best hand. I agree with your decision to fastplay this hand. The full pot sized bet into three opponents indicate, the Villain has at least something, and if he is bad enough to post UTG, he is not going to bet for value and then fold to a raise. You will probably not get much action from the players behind you, but even if you just call, this also looks strong due to his sizing, and they might still fold.
You also have a quite vulnerable hand, which dont mind some protection especially multiway. There is a flushdraw and some straightdraws out there, and there is also a large potential for getting counterfeited, because one of your pairs is so low. A 5 will pretty much kill your hand, and so will a board pairing runout like 4-4, 6-6, 7-7 etc. As for sizing I think, its fine to make it a dollar, but I also think, you can go a bit larger like maybe 1,2$.
Pretty safe card even though you now lose to T9. But thats a very small portion of his range. I would also bet again, and once again I think, you can go a bit larger and still get pretty much the same amount of calls. If he had top pair or a good draw, he is not folding, because you make it 1,5$ or even 1,8$ into a 2,38$ pot.
Pot is 4,7$, and you have 7,75$ left, meaning this is an overbet. Even though you have two pair, you only beat a bluff
, so this is a bluff catching situation. You have shown a lot of strenght by raising the flop and betting the turn, so this does not look like a good spot for him to bluff risking his entire stack. You are also not getting a good price. There are some busted draws, but also a number of hands, that now beat you. He could have JT that rivered a better two pair. Or maybe he backed into a straight or flush with hands like A5 of diamonds or KQ of hearts. So I would fold and live to fight another day. There is an old saying "never go broke in a limped pot", which I think apply here.