Without wishing to be rude, if the car is causing you stress and problems to the extent your worried about going on a long drive in it incase it breaks down you should get shot of it.
First and formost a car is there to do a job, to take you from A to B sometimes via C. If its unable to do this properly, then you should get rid of it.
Keeping an car which keeps having bits going wrong on it going, is expensive. Older cars are much more likely to have bits failing due to wear and tear, and with them not being in warranty you'll have to fork out when bits go wrong.
I loved my S4, but it had done 67000 miles, and a turbo had failed. To replace the turbos, was going to cost about 3000quid, of which over half was labour charges.
I had a difficult decision to make, over the previous year I'd spent lots on the car (Remap, coilovers, porsche brakes, full milltek, cambelt+waterpump service, two minor services, castrol srf brake fluid), but at the end of the day, I want a car which is going to not cause me hassle, and be something I could rely on.
In the end I took the decision that I wanted a newer car with manufactuers warranty so I could have peace of mind, so I sold it and got the CSL.
I now wish I'd bought the CSL a year ago and not spent (wasted?) the money modifying the S4.
What I'm saying is whilst your car is a treasured belonging to you now, and you're very proud of it, if its letting you down, its really not worth the hassle.
Sell it and get something else, something with a few less miles on it, with a manufacturers warranty, and spend your time polishing that instead.
Less Stress = Happyness. Avoid stress whereever possible.