I would be raising a bit more hell if I were you. At this point, you've spent (or are planning to spend) $600 in hotel + incidentals + $200 change fee. Try to make a case with a supervisor and see if they can bend. Suggest that they explore other routings. MUC-AMS-IAH-SFO is showing T availability (T3) tomorrow, 12/2 (translation, wide open). Going AMS-EWR is oversold (Y6). Perhaps the agent you're dealing with is not being creative and exploring different routing options.

Incidentally, as a last resort, you can leave tomorrow MUC-SFO RT (returning as a throwaway in a couple weeks) for $1,100 on the routing I mentioned thru IAH.