Extending the life of a cheap aluminium greenhouse

Hi all, I'm wondering if you could offer any advice for nursing my greenhouse along. It's made of aluminium supports (flat gray metal, not the green tubes) and polycarbonate glazing. It's about six years old. It no longer has any plastic in the roof after recent storms. The plastic sheets are very brittle at this point and my plan to brace them with greenhouse tape and bamboo stakes or similar will not work. The screws/bolts are all rusted, making them difficult but presumably not impossible to tighten. 

I hate plastic waste, but I guess that is my only option at the moment. I'm thinking to either replace with like panels, just expecting the same outcome in a few years; try to find a plastic blowaway cover, although the ones I've found are too small; or try to cover with poly sheeting in some fashion. Is one of these plans actually sensible?

I start almost everything from seed, so I can't imagine growing enough for the allotment without a covered space outdoors. I do have a small grow house/tall cold frame, but I don't think the capacity is anywhere near what I'd need. The thin wood panels are also peeling on the sides, so I keep it in the greenhouse to slow its destruction.

Any ideas for me to grow an allotment worth of plants without living in a fungus gnat-infested jungle for months or suddenly coming into some money and time?