You need to raise from the SB to force the BB out. When you just call, the BB is getting 5:1 to call, which he'll likely to with almost any two cards. While T8s isn't really a bad hand to defend your blind with, you don't want to play it against two villains.

As villain is very aggressive postflop, even if the sample size is extremely limited, I don't think his three-bet has to mean a made hand, but could just as likely be two overcards or even a pocketpair lower than 10. I like the flop reraise, both to try to force the BB out but also to better define villains hand. On the turn I think calling is the right thing, for two reasons. You could very much have the best hand, but even if you don't, you're probably drawing to 5 outs, and you're getting the right pot odds even if villain turned over his cards and showed you aces through jacks. On the river I think you played perfectly. His three-bet probably means he has at least two pairs or better, but the pot is now so large that it would be a huge mistake to fold.

Apart from the preflop call, I think you played perfectly. And if CO views the hand as a classic steal/defend scenario, I think your hand is good almost every time.

Edit: For your last question, I think you either have to fold or reraise in the SB to a steal-attempt. If you are in the BB a call is fine if you have a marginal hand and think the villain could have any two cards.