I have never had the problem with the rear suspension arms, but I've read/heard descriptions. It would certainly be worth raising the rear and shake around on all those joints and there are several to shake.
I really believe you need a little more tire pressure. The pressures listed in the fuel tank door are minimums. I don't, however believe that this is the source of your problem though. With that little pressure you may very well see premature tire wear down the center of the tires, especially the right rear.
Best of luck,