Not sure that I fully understand all your points. Anyway, this is my attempt.

1. You don't need a fast-track voucher. Just show your F/J boarding pass before entering security. And it usually does not make a significant difference. You should have received your BP for all flights wnem checking in.

2. Unless you absolutely want to go to a lounge on arrival, I don't understand your sequence. The normal sequence would be to go with all the arriving pax once you disembark. Then you clear immigration and exit. No need to be escorted.

3. Normally yes.

4. SHould be no problem in that direction CX to BA.

5. Your expectation onboard should be similar to before the pandemic. Personally, I have found the new crews very eager to serve, and most of them will have enough experience by now.Of course, you can always hit a bad crew/FA. There has been threads on the J experience that you can look at.