Complete this old adage...
"When in doubt, d***"
So I'd be taking the Ford to another mechanic if I were you. You've already exhausted the knowledge of one.
Your friendship has nothing to do with how this Ford is going to pan out. So if you buy this car now with all it's 'question marks', you're taking a 'shot in the dark'!
There have been TT/ACA stories before albeit in the 90s, about 'lemon' cars; and there have always been Fords amongst them including prime movers. My brother-in-law is a Ford man with a Mondeo, G6Eturbo, XR6 & Focus Ghia in his family. 3 of the 4 have had intermittent problems, but it's interesting to watch how he still persists and not consider anything else.
Personally, you wouldn't have started this thread unless there were doubts; and several posts further on, you still have them.
Put it this way: if your body still ails you after seeing a Dr, would you seek a 2nd opinion? Preferably a specialist? Know a Ford specialist? You know: the one who's lost his hair?
GL