1) Doesn't make any difference other than---if you set all chargers to AGM setpoints, your chassis battery will also see those voltages. Not really an issue
2)Good but you need a fuse between controller and battery, too.
3)Get a solenoid based isolator instead of solid state, they are more durable and have less voltage drop.
4)When you are unconnected from shore power, you'll want the converter unpowered. Choose an easy way to accomplish this.
BTW, clean up those connectors.
5)May be a good solution as it eliminates the radio's standby power draw and may filter some RF on the incoming power wire.
You still have a lot of unknowns between bullet items #2 and #3. All of those red wires in the distribution panel will need to lead back to the battery positive. A large wire should be used along with a proper lug termination. A battery fuse that considers the whole possible system draw will also be needed. This fuse should be within 18" of the batteries.
A good ground termination will also have to be designed with final ground point leading either to a frame ground pr back to the batteries. The ground lead should be the same size as the larger positive lead to the batteries.
The existing battery wiring depicted in your picture should not be reused. It is substandard for your new installation and will be throwing a lot of power away.
