Replace failing N3150 with NovaKool R4500 compressor for better heat performance or Norcold N3141 for absorption drop-in. NovaKool better for boondocking with solar, absorption for propane versatility.
Avoid deep water with RVs. Water in engine causes catastrophic damage. Know air intake height. If crossed, check all fluids for water contamination.
Your 12V DC AC dual power design is sound but upgrade changeover switch from 20A to 60A minimum. Use 4 AWG wire for short runs, add fusing at both power sources, and ensure proper isolation.