With the dynamics which I don"t pretend to understand I could be way off the mark but here it goes. I think villain puts you on a decent hand if not premium hand to be 3 betting utg+1 against a tight utg raiser, albeit as I undertand it he probably would have raised bigger with a big pair. He doesn"t necessarily have to have a premium hand to be 4 betting here but needs to very playable e.g I dont see many eights in his range.
I always struggle to to put donk bettors on a range but I guess after you have also bet the 8 on the turn (which is not likely to improve either hand ) he must put you on something and have something to be calling. Id put his likely range something like AK,AQ, KQ KJ, QJ,JT,JJ,TT or AJ/AT spades. A fair range of these just rivered you. I dont think you can get much if any value here and I think few hands that are beating you will fold to a bet.
For me its a check, hope for a check behind and review depending on size of river bet. (sorry if thats an opt out).
