Hang in there...CV joints and exhaust systems are consumable goods and can't last forever.
I know how frustrating this can be, and I faced these kind of problems all the time during my restoration project.
I just finished restoring a 1981 "S" and had to replace quite a few things before it was reliable.
One of the smartest things I ever did was use a donar car for my project, saved me mucho $$$ when all said and done .If ou plan to keep the MK1 for some time to come you might consider this approach if feasable for you.
Good luck! Don't give up!
David
1981"S"
1980 donar car......now 16v transplant