Personally, I would take the snake and forget the tank. Half of the problem will be solved that way. Is there any heat gradient in the tank? Poor little guy looks very stressed! Maybe you can do a temporary set up until you can get him into a appropriate enclosure? Any thing that you can put together will be better than that dirty infested tank he's in now. Definitely quarantine him in another room for sure! Make sure you check to see if he is wheezing or has any noisy respirations. Check for mites and wear gloves when you pick him up or reach into that tank. Good luck and kudos to you.