1. you are correct at looking into wheel psi ratings , to match the new tires pressure rating and width are often overlooked. There is some wiggle room , but i'm not too sure about 80# E tires on 50/65# rims.
2. 3x ? you might have another problem other than China.
I would have a 'tire expert' ( I know, that's a loose term) inspect the tires to see .....road hazard or heat related.
If one blew then the spare blew on that same wheel , then I would think something is wrong and NOT a road hazard.
It might be overloaded on one of the axles creating a heat issue ?