Combine Lights on one switch and remove smoke detector from switch
Pigtail the wires going to lights A and B together with a short 6" wire, and send that to the pole of your new switch, and supply the other pole with hot from the breaker. 

Send the wire going to the garbage disposal to a pole on your other switch, and supply the other pole with hot from the breaker.

Then just send hot from the breaker to the smoke detector.