I cannot imagine another ebay set will fit any better. They're all shitty. My worry is that the threads in the head were already stripped enough to pull the studs out when you attached the catback section.
Ugh this is a tough spot. Can you try disconnecting the catback section, then re-snugging the nuts on the head flange? I'm really worried that they're toast, but it's worth a shot.
If you can do that and fire it up without leaks, then maybe you could cut through the piping in the catback section (like 6in after the flanges) and drive it to an exhaust shop like that and have them massage the pipes back to fitting.
That's really my only guess at this point. I'm super worried about the head.
I (of course) have a set of those headers in the garage! I bought them on sale and it came out to about $320 shipped. Really excited to mount them up and should be able to mate them to the rest of the exhaust by changing the flanges out for these:
https://www.amazon.com/dp/B0015KZL1M/
I was hot on their full system, but you have to do a lot of cutting/welding to make it work with the 6 speed and people still had a ton of fitment issues. Great reviews for the headers themselves, though.