Formalin is not just for hardening (it would work better for that purpose in more alkaline pH's than stabilizer is) --- it is/was for stabilizing dyes!
AFAIK, the official process ECN-2 has NOT changed... So whether the films have changed so that they "work" with current C-41-style final rinse or not, it will be very hard to say for sure.
If you can source ECN-2 developer, you could probably source ECN-2 final rinse, or if you can source raw chemicals for developer, then you probably can also get formalin. OTOH, if you are cross-processing in C-41, you already use a wrong developing agent to begin with which may compromise the dye stability anyway.
I can't see how remjet removal is relevant to dye stabilization at all. You should scrub it off as the first step of the process (after softening prebath), but with careful agitation in spiral tanks, many people have reported good results by removing it at the end of the process. This way, I'd do it during final wash, before stabilizer.