As an old guy who has to deal with things like old tractors....
I would like to suggest a picture of mechanical advantage which might work...
Stick something the correct size into the item needing to be broken loose...
Extend with pipe or long enough handle to a spot going towards the front of the car in which access is available straight to the floor.
Use a piece of metal to fit under this extension ( since we are dealing with a right hand thread this end needs to travel UP to turn it the correct direction ).
Then place a hydralic jack under this downtube and wrap duct tape on both ends to keep everything in line until they get under pressure..
Then just pump on the hydralic jack.... Keep fingers out of the way and always wear goggles....