I have been doing some minor remodeling, involving an electrical outlet and wall switch relocation. In verifying the circuit info labeled on the service panel, I discovered that one 15 amp breakers was servicing no fewer than nine light fixtures, a bathroom vent fan, and about 12 wall outlets. Four of the outlets are switched and used for lamps. Rooms fully served include one bath, three bedrooms, living room, hall, and lighting for family, utility, kitchen, and front porch.

I also discovered and verified that I have a dedicated 15 amp circuit for a disconnected doorbell transformer, which seems a bit odd to me. I was planning to reduce the load on the other circuit by switching some of it to this breaker. But I would like to know if I should just dedicate it for one use, lighting or outlets? Or have it service specific rooms? Any thoughts available?

Additionally, this 1,150sf ranch house was built in 1972.

A dedicated circuit for a doorbell is a waste. If you are going to incorporate that circiut into what you have consider making the bedrooms new circuit with ACFI breaker. Whatever serves the bath room needs GFCI protection and you can do that by making each bath outlet and fixture to run off GFCI outlets.