Oh actually, on day 252 of the last scenario (puffball giant Charon), Charon overtakes Kerberos as their orbits come close, which draws Kerberos into a new steeper orbit that I think will lead to another encounter later… yep at about 279 days… near miss… even closer on day 300… then on day 324, Charon closes but is ahead in orbit… then they’re out of sync for a long time, so missing, and it looks like the diameter of Charon is a bit under Kerberos’ orbit, so they may be stable for quite a while…
Oh, I accelerated the simulation, and then about 2.25 years later, after it seemed stable, suddenly Charon flew away… I think it got too close to Pluto and was slingshotted away by the 8x heavier planet, but the simulation was running so fast I didn’t catch it.
I tried running it again, and yes the positions of the other moons matters. This time, Kerberos hit Charon pretty early, and the other moons got new more dispersed orbits that turned into slingshotted wide orbits eventually, but Charon and Pluto seemed pretty stable in a more regular orbit except for crazy fly-bys by two of the remaining moons.