I don't know if this will help, cuz it sounds like this is a pretty hard problem to deal with but here are a couple things...
Tea Tree oil - we once had what looked like fleas (though we were too afraid to think of it) around the house and getting bites around our ankles and all...so we reached for the tea tree oil and started putting a ring of oil around our ankles and putting it around other places too (if it is pure oil and not the thinned stuff mix a few drops into a cup of water, put it in a sprayer and spray on yourself, your dog, carpets, bedding, where ever you want) that seems to work they have never been back...I guess they decided there was better food else where. A drop goes a long way so don't choke if you have to pay close to $30 for a small bottle. You might also want to try eating and feeding your dog more garlic fleas don't like the taste.
Well I truly hope this isn't completely useless but like I say I don't know.