Hate to say it. I'd look for another. Hopefully you can recoup some of your money from parts. I just cut up one in better shape. I don't like cutting nothing that has potential.
With the cheap availability of Spiders in the USA, I'd be looking for another with a clean shell (ie. no rust). The one you have can be repaired, but the time, effort and money you would need to outlay doesn't make economic sense when you look at a replacement cost.
I would be leary of driving it, much less repairing it. I just made a Lemons car out of one in better shape that someone gave me. Please reconsider sinking any more money into that thing.
1972 124 Spider (Don)
1971 124 Spider (Juan)
1986 Bertone X19 (Blue)
1978 124 Spider Lemons racer
1974 X19 SCCA racer (Paul)
2012 500 Prima Edizione #19 (Mini Rossa)
Ever changing count of parts cars....It's a disease!