It would be a good idea to read the FAQ's on the AL-KO website, last one in particular.
http://www.alkoesc.com.au/escfaq.html#.VIoleZMiPmg
Also under the top heading of literature you can download a copy of the User Manual if Jayco didn't provide one. Useful info there with basic wiring diagram.
As to using a resettable circuit breaker for the feed I was advised by a credited installer that it should NOT be an auto resetting type as if a fault happens then it may continue to draw a large current and flatten the battery or burn out wiring.
Personally I think the system should have a connection that can be taken to a display in the car to indicate if the ESC is operational rather than just the LED's on the drawbar. Our ESC failed during the last leg of a trip due to a connector under the van coming apart and we therefore had no indication of it.
I'm no expert by any stretch, but Ive also had plenty of contradictory advice from so called experts to make my own inquiries for my peace of mind.
What your installer says is interesting, because I had the same concerns about auto breakers, enough of a concern to contact the manufacturer. It was explained to me by the Narva tech that by their function, they wont reset if the problem that causes the overload continues to exist, they simply remain open. The upshot of that advice is it would be unlikely to drain the battery, nor cause a fire because they don't reset if the overload continues, and there no load to the device. The Narva dude insisted they simply don't do what your guy is suggesting. That kind of makes sense to me, because what would be the point of a circuit breaker, (auto or otherwise) if it doesn't actually break the circuit .... for any circuit that requires an auto breaker ie the brake controller, I may as well just wire it direct, because by your installers advice the auto breaker provides no function or value. It would be interesting what he recommends for the brake controller auto breaker, and it the advice is different to the ESC, why so?
The point of the auto breaker is to eliminate complete circuit failure in the event of a non catastrophic overload .... in the event of the catastrophic or continued overload, auto breakers stay failed (ie open) just like a non auto breaker or fuse. My understanding is any device connected via an auto breaker, on a circuit with a catastrophic/continual overload; the device most certainly wont be working because the load is stopped at the breaker. So if its not working how does it drain the battery or cause a fire as theirs no load.
As per the reasoning behind brakes controllers required to on auto breakers, it makes sense the ESC functions and is safe guarded similarly.
Going back to my open line: I have no real clue, but your guys advice seems odd, and contradict the identical reasoning to use auto breakers on brake controllers, the function of auto breakers and the advice of the manufacturer.
