Ugh, rust. Level of effort/cost to repair?

Despite largely salt-free Virginia winters and being garaged for the last 10 years, my GVR4's New England origins have finally caught up to her. While the car is surprisingly rust-free almost everywhere else, the passenger side frame rail is all kinds of messed up. At what point is it unsafe to drive / will fail inspection? Any ideas how much this kind of thing would cost to repair? I'm pretty sure my welding skills aren't up to the job. My gut feeling here is that a part-out is coming but I have been through so much with this car I hate to do that.

Front frame rail:

Rear:

Looks like it's rusting from the inside out and the chassis is actually splitting in two:

Thanks!

Man would hate to see that car get parted out. My first E21 was worse than that and I managed to save it with no body working experience and making all the patch pieces( entire floor/framerails/rocker panels) by hand. Get a welder, do lot's of practice and this winter start the surgery.

How much do those affected areas matter in terms of safety/structure? I have a crummy flux core MIG and an entry-level TIG welder that I'm learning on but I'm not confident enough in my skills to repair something structural yet.