When reclassing to a new MOS, is BAH based on my location or dependents location?

BAH is based on your permanent station. If your reclass is a PCS, then you will get BAH at the new location. If it's TDY and return, then your BAH should be based on your permanent location. So you just need to find out if your orders are a PCS or TDY. If less than 6 months, it's probably TDY.

Depends on the new MOS' training length. If training is 20-weeks or more, this would be a PCS and if your family does not PCS with you, you can request a BAH waiver for dependents current location.

25S is a PCS move.