My dad had 2003 Ford Econoline with problems similar to yours, but not as bad. Dealer claimed they replaced the PCM a few times. Ford even called in the engineers (experts) claiming they for sure fixed the problem. Dad didn't even make it 10 minutes from the dealer after the dealer promised they fixed it for sure and the check engine light went on.
Give them one more shot. Make sure you keep all your slips from the dealer from when you took it in. Sounds like you got a good shot at getting a new car through the lemon law. My Dad filed and won, after the Ford engineers could not fix it.
The electrical problems it sounds like you have are very hard to fix. Dealer will likely never find the real problem. They likely never replaced the wiring harness since it's major work to replace it. Where as a PCM is a 5 minute repair.