You need to have a thermostat hooked up to your heat source to monitor the temps. To get accurate readings of how hot the temp is getting - you should get a temp gun. The PE1or2 is a cheap option for a temp gun. Walmart carries the accurite temp/humidity gauges - they are about $12 bucks.
Please keep us posted on what the vet says. I am very concerned for your snake. Respiratory infections are nothing to mess with.
But, if you don't address the proper equipment issues - your snake will continue to get sick from lack of proper temps and humidity.
Given your age and money issues - I would honestly suggest that after you get him well again to give him to someone more equipped financially to care for this snake. Vet bills can get very expensive and getting the correct equipment is pricey too.
Later in life when you are a little more prepared - you can always try again but don't let this snake suffer any longer please.
Best of luck to you.