Scooby getting sores?

[Scooby4]

I am worried about my dog Scooby. I know that he is allergic to fleas. My ferret brought some in recently. Which I've got the issue "contained" but NOT cured. I give frequent baths to the ferret and dogs. Have treated the carpet and such... I lost my job a few months ago and am unable to afford to buy Frontline for all the animals at this point. So I am doing alot of home remedies until I can get to the vet. It has been doing okay so far.
Here is the issue... I know that Scooby is allergic to fleas and I do give him benadryl when necessary. However, something else seems to be wrong with his skin other than the fleas. I have discovered a few areas of odd skin "ailments" They concern me because they are NOT flea bites. One area has my deep concern. It is actually "torn". Almost like a cut but NO bleeding or signs of bleeding. It is about 1/2 inch long. I can't tell how that could have happened. He doesn't mess with it at all.
Another spot showed up today on the back of his right paw. It is a BIG red almost "Strawberry burn" like. I have been taking him for walks recently again. It is on one of those "concrete" walking paths. However, the mark is on the BACK of the paw not near any "rubbing" areas.
The last mark has my concern really up. He had a stroke 2 years ago and is partially paralyzed on that side. He doesn't have much feeling in his right legs. The front one hasn't recovered but to about 50% while the back one is about 75% with feeling.
Could this red mark be from our walking? or could there be another cause? He really enjoys the walking but with his lack of feeling I feel I may be overlooking "damage" being caused. He did get tired sooner the other day and we had to stop the walk half way. The other mark that looks like a cut isn't on his right side. It is on his left and I don't think it is in an area where he is able to scratch it with his paw.
I am very concerned and wanted to see if anyone had similar issues and had some "home treatments'. I will be taking him to the vet ASAP when I get the money. His diet is good and he is healthy otherwise. Thanks!

[Scooby4]

I think I discovered the issue with Scooby's skin. It is the flea and tick shampoo I am using!!! I took him for a walk today with Shaggy. Prior to walking I put the shampoo on both of them. They like to play in a steam nearby on the trail. I put it on so it had time to work before it got rinsed off in the water. It says to leave on for atleast 5 minutes. It takes about 5 minutes to walk to the stream.
We got to the stream and I rinsed them off. That is when I noticed the red splotches again. I figured it was old flea bites. Later, we continued walking and playing in the stream. That is when I noticed additional hair loss as well. It seemed where the shampoo was the "thickest" is where the hair was gone. By the time we got back to the car there was hair missing off his back end and a little on his tail!!!
The good news is that Scooby wasn't scratching the whole walk! Which was good. I also noticed the shampoo left a horrible smell afterwards. The dogs still smelled dirty like they hadn't had a bath. I don't think I will be using any more of the shampoo on them for a little while. I don't normally use Hartz products. My father had some left over and I had used it.
I think if I start using regular shampoo again without the flea stuff in it, the dogs should be okay. I was panicked for awhile over this.

[Flatcoatluver]

the flea and tick shapoo i put on my dog was getting her skin so itchy and dandruff and stuff, then i switch to medicated and started putting olive oil and her food and now she has no problems

[dab_20]

that happened to my friends dog a few years ago using hartz products. hartz, i have found, is not a good brand.