Have you ever considered a flea insecticide bomb?
You would need to remove humans and cats from the house for a couple of hours, but they are very effective.
Unless bombs are persistent, or you do 2 or 3 treatments, you still have to deal with unhatched eggs. Diatomaceous earth lightly sprinkled over carpet will persistently get the larvae (they look like little tiny maggots). That DE will terminate pretty much anything else too in the insect department.
Funny slide, we actually recovered this stuff on a geotechnical investigation one time and the bulk sample made its way to our lab for a proctor test. A proctor test is utilized to determine the optimum moisture and maximum dry density of soil for use in conduction of field compaction tests (pads, footings, roadways etc...).
When you’re running the test you take the dry material and compact it with various amounts of water and record the density result and this gives you a curve, the peak of which is the optimum moisture and density. The point you pound that puts you over or past the peak is where it “breaks” and you can derive the value.
Diatoms are silica shells, spheres, tubes, etc... and are mostly space. The lab kept adding water to this “sand curve”, and it kept going up and up and never breaking. I think they stopped at 60-70% water. They were pulling their hair out until I posited that it’d make sense if they had diatomaceous earth in the sample and sure enough it was from an area with deposits.
For comparison, a decent virgin aggregate base (a gravelly, sandy mix with low fines used for road and parking lot bases to be paved over among other things) usually has an optimum moisture around 5-8%, a fine sand/silt around 10-15 +_, and a clay from 15-30% (clays have a big range and its highly dependent on type).
I haven’t tried flea bombs. I was under the impression that you had to vacate the house for a lot longer than just a couple hours. Also, the idea of re-doing it periodically to get the newly hatched eggs. It would be hard to get the cats all outside on the patio, invading the space of the ones that live there, it would take all of my energy just to supervise them there - of course de-fleaing all of them beforehand. Not to mention getting the spouse to leave the house for that long. LOL But if it can be done in 2 hours, I may research it further!