Without proper examination and diagnosis by a reptile vet, your best guess is what you can find online and what people (non-vets) can try and suggest. Giving the wrong meds and the wrong dosage can kill your snake, and you won't know that you overdose your snake immediately because of their slow metabolism until it is too late.
I have heard of raising temps and/or humidity, but your best bet is a vet. Have you tried your closest reptile rescue for help?
Unfortunately I agree that surrendering your pet or making the travel to a vet may be necessary. Not that this a slight towards you, but seeing posts like this is heartbreaking because planning for a pet always requires planning for a vet. Animals will inevitably get sick, and medical care (access and finance) should be the first thing on your list prior to purchase of any pets. In the end, the pet suffers longer than necessary and the owner feels the loss of the pet either to illness or having to give it up to a rescue who can save him. That latter option is hard, but if that is what it takes to get him better, then take this a lesson learned and do what you have to do for the snake's best interest.