One of your major problems is trying to run the refer (20-30 amps) while driving. Whatever else you do you should also fix that. Try adjusting the metal shield around the burner to eliminate gaps. On my last camper I had to tape up a few of the vent holes near the burner in the outside cover. This requires some experimentation, there is probably an aggressive eddy entering the cover somewhere.
Very heavy wire from the truck will make only a small difference in recharge times, because lead acid batteries will only absorb very large currents for a short period. Something like #8 (and connectors to match) will do most of what can be done. If you go to #2 you may get more current for the first 1/2 hour or so.
