Nightmare with hitch mounting points

[NoTyme]

2009 RXV Fleet
I changed out the rear bumper due to it being cracked and found that there are 2 bolts on each side going into the frame that hold the rear plastic bumper in place. The ones towards the rear are turning in the frame (they are pressed into the frame style nuts). There is no way to get inside the frame with a needle nose vice grip with the bumper in place so I have only one bolt on each side holding the bumper in place (besides the torex screws from above).
I am leery now because I want to install a hitch and those two bolts that are NOT spinning in the frame are the ones I need to undo to mount the hitch. If one of them (pressed into the frame nuts) start turning I am up a creek…
I tried to tack weld but they may be aluminum or cast and it did not work. Maybe the pressed in nuts are replaceable but I would be able to press them in from the inside of the frame.
Any thoughts would be helpful. I am out of ideas.