As for the bolts, forget wrenching. I bought one of these for that exact purpose (6A, 4 1/2" for $29 at Tractor Supply). Don't forget a pack of cut-off wheels and safety glasses. We were whacking off 1/2" bolts on our dock hardware back in April. But work carefully to not damage the trailer, and replace one at a time. Cut through the nut about 1/2 way, then use a long breaker with a socket to twist it off, and pop the bolt out.
My bigger problem is dragging the rear cross member "v" when I transition from downhill to level. The weld is still ok, thankfully, but it would be unwise to keep grinding it into the pavement. So, my solution is to bend a piece of 3/16 steel to match and (square) U-bolt it in place below the cross member. Then, to keep the pavement pretty, I might cover the steel with wood as a sort of sacrificial member. Ugh, the things we go through...