The fleas have been a real pest this year. You've tried all the alternatives but one more you can look at is Bioganic spray. I'm not sure where you can get the solution in a spray bottle but the hose-end can be found at any Lowe's. It won't hurt you or your dogs. I used it recently and was very pleased. You could also use a hose-end container on your outside area as a control measure. I mixed Bioganic in a regular size spray bottle at 1/3 product to 2/3 water and it seemed to work well.
Fleas will get in any crack or crevice and hide to lay eggs. I'd vacuum the heck out of the carpet and spray with one of the products to kill everything that is still there. Use your vacuum on every square inch of your house, and suck up a little DE before you start so you make sure the fleas you get up are killed. Vacuum every day for 3 days and then every other day and you should get control.
As for the sore spots, tea tree or lavender oil or a corn meal poultice will give great relief. A corn meal bath works well too. Sorry to hear the poor pooches are suffering, but I know you are too.
Hope this works for you and you get some relief!