Advice on weight gain for underweight snake

[Dandelion]

Hello, I'm new to the forum. I did some poking around but I haven't been able to find an answer to my question. So here I am hoping someone can help. A little history. I've been keeping colubrids for a few years now and have really enjoyed them. I decided to take the plunge and get a boa. I live in a bit of a remote area but I watched craigslist for a few months and a young one came up. I went to check it out and the people keeping him were not doing a very good job. He had mites and is underweight. I talked them down to half the price and brought him home realizing that it was more of a rescue situation than a healthy adoption. There isn't a reptile vet within 200 miles of me but I talked my local vet into checking for parasites aside from the mites and he was cleared. Obviously he's still in quarantine but I believe I have destroyed the mite situation by following the anapsid websites advice on killing mites. I used ivermec as mr snake was and is bright eyed and active. But still, I am sure he is underweight as there is a lot of loose skin. I don't know for sure how old he is but my guess is not over six months. So, two things: is there a chart for length and weight guidlines for boas and what would you all recommended for a feeding schedule to regain weight? Feed as normal? He's taken two meals of hopper mice now in the last two weeks. The people that had him were feeding him large adult live mice but I felt like that was an awful lot for the little guy. Thanks so much for any input!