first, I really hope this is in the right place, I'm stuck on mobile so it's a Tad difficult. I desperately need some help... I've been reading the forums longer then I can remember, Ans besides personal experience over the past 5 years I've gotten. A lot of info from here but never joined... I'm to a point where even with my experience I know not what to do, so for anyone that reads or replies thank you in advanced...

I just recently acquired my Super Pastel at the NARBC show in Tinley back on October 8th, he seemed healthier then could be, no bad scales, scars, not even the smallest signs of mites, he seemed like a jewel. And with a price tag of 100 he was.. I made my worst mistake... I didn't write down the breeder I got him from. So i toke him home, a 2 hour drive. He seemed fine on the way back, just he liked to explore. When we arrived he was still doing fine,but for some reason about two days later he started to drool, and his mouth had bubbles, the beginning signs of a R.I or mouth rot. He was scheduled a vet appointment 4 day later which was the earliest the vet could put us in. This is a vet certified in Reptile care as well, and the only one within 90 miles... at his appointment all the vet did was pry open his mouth.. which nearly killed my snake, and listened to his heart. After that we were given a mouth wash for cats as She said "I see no positive signs of infection" at this point though you could see the "cottage cheese" inside his throat. So.. 3 days later I call saying that he's got worse and get a appointment the following day. This time I was told, "this medicine Is for a R.I. and can also treat mouth rot" I forgot to mention we called Because of rot.mouth beginning to develop, sorry it's hard to go back and edit from the phone. The medicine for his mouth rot/R.I was 7 shots of 1.5 ml of something, I'm at work and will update the exact antibiotics and dosage asap. But it has been a full 21 days and 7 shots. His mouth rot and the "cottage cheese" within his throat have cleared, but not his excess saliva. Luckily it only cones out of his mouth and not his nose. And to my.knowledge he has mites, the mites came from a local pet store.... which I am sure of. My question, what can I do now? I went to a local pet store that is actually reliable and there best Reptile expert said all she can think IA the snake was loaded with antibiotics to appear healthy to be sold and she thinks I should put him down. I really don't want to do this....... I've spent nearly 400 in vet bills and I have really come to love him... can anyone help me with some advice on treatment or even a personal experience? I can't afford another Vet bill... nearly $100 to have someone who knows less about snakes them me say "your snake is sick all right" then even more for medicine which probably won't even work again.. my final bit of info would be his tank. His bedding is newspaper, and He has a water bowl larger enough for him to soak in and to hide under. It is a cats water bowl that was bought just for him. He has a 150 way day bulb which gives a temperature of 90-100 depending on the day outside and a night bulb of 100 wats that gives a temperature between 75-85. His humidity stays between 40-60 And rarely falls below that. That's honestly everything I can think of, I tried to be as detailed as possible. Again thank you in advanced and I will get medicine And dosage later today after work.