Drive it until you are sick of driving it or until something major goes wrong, then part it out. I hate rust, it is really a PITA to cut out panels and replace them. Collision damage is one thing, rust is just nasty unforgiving stuff. It takes a great deal of experience to repair rust like that correctly, along with a rust free donor car usually.
Think of all the work, frustration and money-consider the value of the car VS. simply driving the snott out of it until you find a screaming deal on a better one. Maybe another solid shell with a blown motor/trans and swap out your motor/trans/interior. You should be able to part that car out fairly nicely and allow its spirit to live on through the act of helping others keep their cars in better repair (and monitary gain to if you want to look at it like that hehe)
