I definitely fold pre with this hand when facing a 3 bet. Calling puts you in a lot of tough spots postflop with a dominated hand.
In appropriate circumstances, calling with QJs might be ok, but I really don't recommand it at 10NL. To flat 3 bets, even in position, you have to be able to bluff / semi bluff and have a good skill advantage to make the play profitable. Considering that you will mainly beat 10NL my value betting correctly instead of running big bluffs in bigs pots, I think that simply folding and opening a little less from CO when this player is in the blinds (as mentionned by the previous poster) is the best solution. Also, you definitely flat hands like TT-JJ as a starting point.
4 bet bluffing isnt a bad idea, but I prefer to do it with an Ax hand (blockers). Altough, I prefer to have a good sample size (1k hands+) on vilain before starting to make these moves. I want to be sure that he is really 3 betting wide and can fold to a 4 bet.
Your flatting and your 4 betting range will depend on differents factors.... how often vilain 3 bet, fold to 4 bet, how he plays postflop, how you are capable of exploiting him postflop etc...
As how the hand played postflop, I think that I prefer flatting flop. Raising the flop vs his cbet is really really thin value. To do so, you have to be certain that vilain is 3 betting and cbetting a wide range and has enough draws in his range to call with a worse hand. By raising, you are likely to make vilain fold most of his bluffs except those that have good equity vs you. Some aggressive players do it because they have an aggressive image and they know they can value raise thin in theses spots (but you see it at higher stakes mainly). Personnaly, I prefer to flat, plus, I don't think you need to worry about value raising thin to be able to beat 10NL.
I prefer betting something like half pot OTT for value and protection.
OTR, there are 2 ways to see it, depend on the level vilain think :
1- He checked behind OTT, he has a weak hand, so let's push him off his weak hands.
2- He checked behind, he have some SD value then. Try to extract the max from him.
Personnaly, I think his line looks weird, but he could easily have some Tx in his range here..... I really depend on what you know about vilain so far. You are really bluff catching here and this is probably close. I would lean toward folding here when facing a pot size bet OTR, unless if he his on the aggressive side, you could probably call and take a note on him. So far, we don't have much information.