I'm not sure that I'm understanding all this but are you know complaining that you let the car go so cheap? You didn't have to, you could have simply put your reserve to any # that you wanted or sold, traded the car by other means.

You also sound as though you're now sorry that it's gone. No one forced you to sell it either, your choice.

Now, have I ever endured major auto related headaches? Yep! Did I then give up and sell the car, nope. If you like something enough, you learn to grit your teeth and push past the irratations until the problem(s) are eventually solved and sooner or later, anything can be fixed one way or another.

The C70 Coupes were not unusually troublesome UNLESS you ever needed to have a window cassette replaced, then THAT could be a real bummer if not done correctly and there's nothing easy about that job.
The early C70 convertables on the other hand were/are far more troublesome overall and I'd never advise one to anyone that I liked.
I've never heard of any X70 (any) with a leaking windshield problem so to me, that's unusual but I'd think that any decent glass company should be able to replace it w/o problems the first time.