The only sure way to find out is to have the fault code(s) read. It seems very unlikley a FAP-related problem would affect your cruise control, as mine continued to work, even with the engine in limp mode. This means you almost certainly will find multiple problems.
Personally, I would remove the FAP physically and in software, note and reset the fault codes, then see what comes back. This would also give you the chance to diagnose your cruise problem the easy way. It's also strange that the additive fault went away, normally they lurk about and plot your downfall. As I say, de-fapping may not be the full answer, but it's a question of when, rather than if, you need to do something about the dpf.
As you're an established member, I would happily do this for you FOC, but don't know if that's practical distance-wise. Alternatively, get yourself along to Pugfest on the 14th for an unusually worthwhile day out.
Anti pollution fault simply means any engine ecu related fault, (guessing the marketing guys triumphed over common sense).
Without knowing what's up, it's impossible to tell if it will worsen or when - if it's an intemittent fault, it may even go away itself, (but would still be logged).
