30amp RV electric Help!
Do not replace a 15A breaker with a 20A breaker. Breakers are sized to protect the weakest part of the system and if that is the wiring then using a larger breaker creates a fire risk.

If the original design was planned that none of the loads would be in use at the same time ( a poor plan imho) then a 15A breaker may have been (incorrectly) deemed sufficient.

If you want to split off the circuits then add 15A breakers but check the supply side wiring to make sure that it is sufficiently sized to handle multiple loads.