E70 Rear lug nuts came loose/off

[Ozer]

I was driving home from an out of town trip and noticed a slight vibration on the steering wheel after leaving the mall (had it valet) so i was trying to listen/feel and diagnose it. Stopped couple times, checked the wheels lug nuts and nothing was out of the ordinary. It got little more intense and i could pinpoint it to the left rear wheel, checked the lug nuts and they were almost coming off. Doing 70+ on I90, this could have been a really bad day.
Anyways i tighten them up and after few miles it did it again. So i kept doing this all the way home, i think the bolt holes got enlarged because at some point (close to home at least) i lost 3 of the 5 bolts, barely limped home and parked it.
I cant remove the 2 bolts with a breaker bar and a socket, i don't want to break them. Its getting towed to my shop today and see what they can do. I'm thinking the rear hub needs to be replaced? (anyone have a DIY they seen?)

A week ago i did the rear brakes and torqued the wheels to 100ft/lbs, only the rear left did this. Right side is still tight. Anyone have an idea as to why this could have happened? I know i torqued both sides so that's not the issue.