Itchy ears/losing hair

We got Zorro after his owner died.  Initially, we thought he was stressed after he started chewing himself.  Once I noticed he had raw sores on his backside, we took him to the vet.  She gave him steroids and told us to give him benadryl to keep the itching away.  She said if it's allergies it could be anything; he was negative for fleas or flea dirt and whatever else she was looking through the microscope for.  He was very new at the time and we didn't have his records.  Still don't.  Anyway.  That cleared up and he started getting comfortable here.  Now, he's a pleasure!  However, he has recently started pawing at his head/ears incessantly!  Also, he is losing hair along his tail.  He's not chewing himself raw like before, this seems different.  I just put another frontline on him in case the fleas have picked up.  Still scratching.  I started giving him benadryl again to see if that helps, I think that just makes him tired.  I tried searching the internet and ear mites keep coming up.  I can't afford to go back to the vet right this second so I looked up home care for mites.  A lot of sites suggested a few drops of olive oil and vitamin E and/or grapefruit seed extract.  I have these things here because I make soap and lotion and things.  I started putting a few drops in each ear last night and it does seem to offer him some relief for a little while.  Sorry this is so long.  My question is:  Is it possible it's ear mites?  If so, will this remedy work and is it safe?  How long until he's free of this using this method?  Other than the pawing at the ears and losing hair on tail he is eating, pooping and seems happy.

[Dan Sims, DVM]

Flea allergy sounds likely so i would put him on comfortis and after 8 weeks if there is no improvement a trial with a hypoallergenic diet is indicated.
Ear mites are rare in adult dogs

[callalilybeauty]

Thank you so much, Dr. Sims.  I will definitely try that!