Inverter: Where to start? Subpanel or No Subpanel?

Thanks in large part to the community here, this new RV'r just finished his first mod, e.g. creating a new battery location and replacement of the power converter/charger. My next project is installing or at least "preparing" for an inverter installation. I'd like to do as much of this as possible as to control cost, but under no circumstances do I want to sacrifice safety. If I can get this most of the way complete, I'd be a happy guy.

Here's the scoop...

The scope is to install,(as much as is safe) a 12v Cotek 1500 PSW inverter. This inverter has an internal transfer switch and AC breaker. I want the inverter to power all my coach outlets except for A/C and the Microwave. I don't want any manual switching here at all, rather, have inverter setup so it acts much like a UPS in the absence of shore or generator power. Likewise, I want the inverter to bypass should shore or gen power be available.

For reference, my AC panel already has the Microwave and Air Conditioning on their own breakers. The remaining coach outlets (the ones I want on the inverter) are all on the same breaker including the GFCI outlet in the bath. This breaker is also wired to my converter/controller with what appears to be a pigtail of sorts (pic below).

Pic of panel

Pic of breaker w/pigtail

Questions

• Since the coach outlet wiring is already isolated, do I need a subpanel here?
  
• Do I need to separate the house wiring from the exist breaker that also shares the controller/charger?
  

Again, if I need to pay someone to do this, I will. I'm just trying to save as much as I can and move the project in a direction that I know is both safe and effective. The last RV shop I went to was going botch this whole thing and I just want it done right, and for as little as possible.

Thanks again for your help.

Tim