The GRINDER is your friend.

Not a hammer. Not a baseball bat. A GRINDER!

Apply frozen wet towels to outside of fender opening to protect the paint. I tape mine on, with the adhesive far from the heated area.
I take it off in quarter inch strips—keep grinder moving along to prevent excessive heat.
Be sure to go all the way past “10 and 2” or else you’ll be doing it again. (Ask me how I know!)
Do this with good ventilation around back of the car.

Eastwood fender roller does not work on rear fender openings due to the double thickness that you’ve already noted. (Again, ask me how I know!)

Left side usually rubs. Normal…(get ready for TKO to write a dissertation on that)

All Versailles rear ends I have dealt with are built that way. To correct it requires elongating (sideways) the locating holes in the axle perches so you can relocate the axle sideways. It will need to move sideways about 3/8” to center it.

Even though a grinder might get you some clearance, the rear end will still not be centered under the car and you risk introducing a pathway for water to get between the inner fender well and the quarter panel.  I woul NOT recommend you doing that.