There is no need to taper Remicade. The problem is starting back up again. The window for restarting Remicade is usually considered to be 16 weeks. If you go past that then your chances of having a severe reaction go up. That said, other people have gone longer than that and been able to restart with no problem.
Can't say if you will flare - not everyone does just because they miss a treatment.
If the infection in your arm is severe (sounds like it) then you need to stop and get that cleared up before it goes systemic. That could kill you or cause you to need antibiotics for a lot longer.
Yeah, the c. diff might come back. But not necessarily. Just keep an eye on it and if you get symptoms get tested right away so they can start you on Flagyl ASAP.
sorry to hear your troubles. Hope they pass quickly and you get feeling great soon.