How had he already sabotaged his marriage?
when he started doing METH! and all that went with it. that is no small thing.
perhaps you were willing to overlook and forgive too much? as it was you were focused on the upcoming vacation....as was he. he held it all at bay JUST long enough til you got to the point of no return. he wasn't concerned about the state of the future of his marriage....only the upcoming TREAT. and now, once again. all bets are off.
he doesn't SEE things as you do.