Yes you are now just on battery for 12v and shore power for 120 so you can get by with some sort of battery charger and no converter for as long as you like.
I don't know how you can have dim /flickering lights with the battery disconnect open (so on converter for 12v) but have no voltage (from converter) at the battery lugs. Mystery.
Don't know if blowing out the dust made that red light change to green, but there is still something wrong even though it is now green.
How about the reverse polarity fuses (two 30a? ) Can't see where they are in the photo in the link above of the fuse panel etc. If one blown replace both. Maybe whatever made the light go red blew those fuses.
You can eventually get a better converter without repairing that one at all, by getting a "deck mount" three-stage type and mounting it near the batteries up front. You can get 120 up front to power that by extending from the front wall receptacle down low into the cargo bay behind that wall. Just take the receptacle out and there is access for a wire you can poke into the bay through some cloth stuff and you are in business.