That car looks barely fixable, and it certainly wouldn't be worth it IMO. Having a car that is significantly more solid, I STILL manage to find more rust every time I look at it, and I've had it for a year. If my car is this bad, yours will probably just be a case where you cut away rust, and you're left with nothing. For a little perspective, my car, which has MUCH, MUCH less rust, I am still planning on replacing with a new shell.
If you decide to get a new shell, you should not just send it to the scrapper though. Part it out. Your car is a series 1, and they have numerous series 1 specific parts. Also will be a great way to get at least some of your investment out of it.