So 2 months and some change in and I think we've worked out most of the problems.
Replaced the converter so the batteries charge.
Replaced both coach batteries with 2 235AH 6V batteries from batteries plus.
Replaced most of the battery cables with new as the old ones were looking pretty rough.
Replaced the engine battery today.
Added a battery monitor as well as an engine temp gauges because the original temp gauge didnt work and I didn't have time to guess what was wrong.
Also added a TPMS system. Attachment 26883
Still haven't figured out how to make the fridge work off propane though.