I apologize if these have been posted, I haven't had time to read the whole thread.
When I was a kid (some 30-35 years ago) I had a Collie that developed fleas. We gave him some treatment or another from the vet, it almost killed him! Most of his hair fell out and everything :-O Since that experience, I'm always very hesitant to use prescription strength drugs unless I know exactly what I'm doing.
My first dog (Pepper) had fleas, so I gave her garlic pills. I know that was on the dangerous side since they're in the onion family, so it was a gamble either way. But she loved the pills and ate them as treats, and within a few days the fleas were gone!
Later on in life, I developed a sudden and severe allergy to ant bites. I discovered that when I had a few bites and ended up in the hospital! So in an attempt to get rid of ants, I bought a bag of food-grade diatomaceous earth that I've spread around the perimeter of the house.
Since Pepper I've had 2 other dogs and 2 cats, and have yet to see fleas on any of them. And I've only had maybe 3 ticks on them, total. I can't say whether they all left because of the garlic pills that I gave to Pepper or if it was the diatomaceous earth, but those are the only two things I've done that might have repelled them. And I live in the middle of about 1,000 acres of wild woods, so you would think they'd be all over the place!