Will my fiancé lose their duty assignment if we get married?

No, he won't lose his assignment. He would have to request to delete his assignment. He will go, unless he deletes his assignment, and you will stay at your current location. Once it's time for him to PCS again you will both be put together

NO, the service will send him anyway, the problem becomes you going with him. 1st thing after the marriage is get registered with the dual Military Program ( can't remember the name). It will NOT guarantee that you are stationed together, but they do try every hard to make it work.

Not unless he waives that assignment. Once you enroll in the Married Army Couples Program (MACP - unless they have changed the name of it), the Army will TRY to station you together for future assignments. If you have both been on station for a short period of time, it is entirely possible that they will just send you to the same place he re-enlisted for. If that is not possible due to timing, slots, or other circumstances, the Army will likely PCS you to an assignment which will line up you and your fiance's NEXT assignment dates, and then PCS you to the same location at that time.

But remember, MACP is NOT a guarantee. It does NOT prevent unaccompanied tours, and it does NOT guarantee PCSing together even on accompanied tours. There have to be slots for both Soldiers available. Your MOS is relatively widespread, duty station-wise, however the NUMBER of slots in your MOS at any duty station - especially once you get higher in rank - is not real high, and the number of OPEN slots is even lower. If your fiance's MOS is similarly small, it becomes more difficult for MACP to find suitable duty stations for both Soldier's MOSs. (And they also have a range, I believe 50 miles, for different duty stations to be considered "together" so you could be at different duty stations, but still considered together for MACP purposes.)