Maybe his skin problem is some type of fungus like ringworm?
I'd be careful with the canned pumpkin, I've heard it's not good for dogs. ...And about the gas...I have a dog that has had terrible stinky gas his whole life, even with homemade food...until I fed him only raw meat..His gas finally stopped. Once in awhile he'll have a few stinky farts..I've just assumed he ate something he shouldn't have... I've experimented around a lot with giving my dogs fruits and veggies and other things along with their meat. .I try not to feed them anything that I will see undigested in their poop..I've seen carrots and watermelon...and fruits and veggies also seem to give them diarrhea sometimes. So now I stick to an all raw meat/bone and egg diet, with powdered kelp and alfalfa and bee pollen granules mixed in with the egg. ..That seems to work well. ...Oh and for the fleas, I give them brewers yeast with garlic tablets. I've had bad flea infestation problems in the past, but now my dogs don't have a flea problem at all... The tablets also completely wiped out a horrible tick infestation we had from a stray dog we brought in..no chemicals needed.