Well it's good that you found it before it got any worse! That does look like a severe burn because of the tbs or(total body surface) involved. It looks like it covers about 1/2 to 2/3 of the ventral scales. IMO, yes the iodine solution is a help but the bp will need supplemental medication to stave off a systemic secondary infection. The vet will take care of that hopefully. Are you sure he is a herp vet specializing in treatment of reptiles? That burn looks painful though. At least he is on his way to healing at this point. Stay in peace and not pieces.