Fleas this summer are the worst I've ever experienced. DD's cat was having seizures that started right after we treated her with Frontline +. We eventually found a solution to the seizures, but then she started having skin issues. we took her to a dermatologist who suggest she use Advantage and nothing else (only product that did not have a history of seizures). She also suggested the seizures may have been triggered by flea bites.
Fast forward, we now have moved DD's cat to live with her at college where the cat is doing great. At roughly the same time, we had to put our 13 yo lab down. Shortly after that, the fleas came out with a vengeance. We have bombed every room some more than once, vacuumed and scrubbed every floor on a daily basis, treated the couches and beds, threw away all the dog beds. We are FINALLY starting to see the end to the fleas but it's been weeks now.
Can't really answer the OP's question except to say to stick with it and don't give up. Anyone who says there is an easy solution I can only say not this year. This has been awful.