2. The batteries need to be isolated to prevent them from simply discharging each other http://vandwellers.org/isolator/index.html
A isolator is required if one battery is wired to the vehicle starter and ignition to prevent you from discharging all the batteries in a worse case situation. If you run down the starter battery you can't get get the rig running and can't get home. If you have each battery on an isolator then you will have multiple batteries, and the batteries can't share the load between them. Only the battery for the vehicle starter needs to be isolated...
then i dont need the isolator cause my trailer dont move nitwit. theres no engine. oh-my-gawd. ha-ha
so, with that new information we will go with all AGMs with the current diagram. we dont need to isolate anything. right?
ps: and yes i have been sleeping above that gel one for over a year and it still works.