Line is fine as long as you fold river almost always. Can potentially bet smaller on flop. Like the check on the turn.

This could potentially be closer against certain regs but you will have a ton of calls in your range so folding here is the right play.

Well played. If you want to incorporate some AA into your calling range then I would call with hands that don't have the Ad as this is a card that villain could conceivably bluff turn with. That being said vs this player type I wouldn't think about blockers too much and would lay this down the large majority of the time

For what thought process you apply: the first step starts with your range and his range.

When you bet flop 70% pot into four players, you're basically saying that you have an overpair, top pair or a set. I'm not sure if you're opening 87s and T9s from UTG, but if so, those are the bluffs you could have. Would you bet AK/AQ/AT on the flop for 2/3 pot? Probably not? Would you bet TT on the flop? Probably not, I would guess.

The turn pairs the top card. If you had top pair (now trips), would you check here? Checking a Jack (at least some of the time) is a decent option, because having a Jack in your hand reduces the chances of your opponent having a hand which can call you. If you have a draw -- something like AdKd or KdQd or T9s or 87s, you might want to continue barrelling, or you can check/call to have some disguised flushes on the river.

So, when you check/call turn, you have either an overpair, a boat or a Jack (sometimes), or something like two overs and a FD. So, your range is something like:
JJ+,66-55,AJs,KJs,QJs,JTs,AdKd,AdQd,KdQd,AdTd,Ad9d,Ad8d,AhJs,AhJc,AsJh,AsJc,AcJh,AcJs,KhJs,KhJc,KsJh,KsJc,KcJh,KcJs

which is 47 combos.

He bets 2/3 pot on the river, so you need to defend about 60% of your range, or 28 combos. If you fold all the flush draws, and all the overpairs, you only have 23 combos, which is about 50% of the combos.

Most people underbluff, so it's probably ok to overfold on the river. If you're betting most of your Jacks on the turn, you probably need to call down with this hand. Your hand blocks AJ and unblocks diamonds, so it is a fine hand to call down with.

As played I would say easy fold on river. However if villain is decent to good and can turn made hands into bluff (99-88-87) we simply need to protect our turn range by checking a portion of our own J's. Basically we need to be mindful how we construct our turn checking range. If villain is super aggro then I can conceive calling with AA which would be a small % of population.

sunshine98 To understand the math, think about it from the Villain's perspective when he's deciding to bet. When he bets 2/3 pot, he is risking .66 pot to win what's in the pot + the 0.66 pot bet. So the amount of fold equity he needs to run a profitable bluff (assuming whenever he gets called he loses) = risk / (risk + reward) = 0.66 / (0.66 + 1) = 0.66/1.66 ~ 40%. Another words, if you fold 40% of the time or more, it's a +EV bluff. Therefore, you need to defend 100% - 40% = 60%. This is known as your "Minimum defense frequency" or MDF.

4way, we are not excited to cbet flop at all. But with weaker player, we might (not always) gain more EV by betting. As far as other said - folding river should be good