first off bro congrats on the babies! i am a little concerned about you circuits thou bro check it ok you have 305 watts of CFLs you are prolly drawing 3-4 amps on just the lights that realitivly little on a 15 or 20 amp circuit as for the computers they draw very little ampage that means that circuit is already mostly loaded although the breaker is a fail safe so to speak you say you live in a old house witch prolly means old wiring i wouldn't constantly push the limit of those old wires. it maybe a non issue but i would always stay on the side of safety. is there any way you can run a extension cord to another outlet that is on another circuit if not shut the breaker down and isolate other devices on that circuit and move them or shut them off.
you also said you are have trouble with heat control . i was wondering where your intake and exhaust was , i don't see them in the picture . ideally in a grow cab you want either the exhaust or intake on the bottom and the other on the top forcing the air to move from top to bottom or bottom to top of the cab. kinda like this pic i drew for you the duct does not have to be in the exact top of bottom they can be coming in from the sides it doesn't matter you just the air to move through the grow chamber and lights and out the room . here is a good STONER TIP when trying to figure out if you ventilation is working properly take a big as bong rip or rip of the pipe and blow it at your plants see how long the smoke hangs over top of them it should dissipate fairly fast . you can also see in the smoke how your air travels in your room. if the smoke is hanging around you gotta rethink your ventilation.
i hope i helped and thanks for stoping by my grow