Holy deathtrap, Batman! I think if someone tried to grind away that rust, there'd me no metal left.

I am a risk-taker so I would drive it, but not to any important engagements. But I imagine it's much easier to fix before it breaks.

I think the best solution might be to come out here to the great state of California, pick up a mechanically worn out but non-rusted car, and transfer all your goodies to the California body. Labor intensive, but rust problem solved.

rust
 

may it rust in pieces.. my buddy has a metro that did just that... someone cut in front of him, he hit the brakes, kaboom, the left wheel went way left.... pulled the cv shaft apart... the lower mount peeled off of what was left of the frame... This thing is a death trap when it happens.. my bud luckily was in town at 25 mph when it happened.. Its part of the unibody, not like the older cars that had sub frames that bolted on the underbelly