First of all, you need to put a fuse on BOTH ends of the hot wire. Both the engine and house batteries are voltage sources that can cause problems if the hot wire gets shorted to ground.
Second, why a circuit breaker instead of a fuse? If space is tight, you could use marine type fuses which mount directly to the battery.
https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A2/0 wire has an ampacity of 190 amps. A 120 or 150 amp fuse will protect the wire from short circuits easily, and never blow under any normal load.
