I have a circuit that is overloaded because it services a dehumidifier as well as our main bathroom. I am trying to find another circuit to run the dehumidifier on. One possible option is an existing (220) circuit that runs into the utility room that is not being used ( it was previously used for an electric dryer). Can I convert this 220 line to create two separate 110 circuits? If yes how would this conversion be done. Would I be able to use the existing 220 circuit breaker or should I replace it with one with lower amps (15 to 20)?
My intent is to create one circuit for the dehumidifier and the other circuit would be used for a freezer.

I do not have access to start at my electrical panel because the walls and ceiling are drywalled so I am limited by that restriction.

If you have 2 hots and a neutral, you can have 2 circuits on opposite phases share a neutral. If no neutral, then 1 wire will be taped white at both ends, connect to neutral busbar, and receptacle neutral.
You need a 20 amp breaker(2 pole if a multicircuit).
May have to pigtail short piece(6"?) of #12 wire to allow connection to receptacle and breaker.