Well, I am about to become very unpopular with you, hon. But, I'm going to be honest, so I'll take what comes.

First off, housing two snakes in ANY size enclosure is a BAD idea. It causes stress, aggression, can contribute to disease and it is not unheard off for the smaller snake to be attacked and killed. If you want to keep these snakes and do the best you can for them, separate them as soon as possible.

Second, a 55 gallon is really much too big for Ball Pythons, period. Balls are shy, secretive snakes who need small spaces to thrive. The random hissing you hear is a sure sign they are stressed out and unhappy. The two you have would be much more comfortable in 20 - 29 gallon setups for each snake. I won't talk to you about tubs because someone else will. A bonus to smaller enclosures is the temperatures and humidity will be much easier to maintain. You should try to go with UTH only, and that is nearly impossible with such a big area. Ball Pythons need belly heat to properly digest food. For the most part, the daylight bulb and ceramic heater only make it harder to keep humidity up, which is why the one shed all in pieces. Plus Balls don't bask like lizards do.

You will want to make sure when using UTH that the thermostat probe is touching the glass over the UTH. Because while the substrate might read 92, the glass could be much higher and that can lead to burns if the snake burrows and comes into contact with the glass.

Hides are easy and cheap. Upside down dishpans, unused oil change pans, clean mop buckets with the side cut down all make ideal and inexpensive hides. Plus they are easy to clean and sturdy. Just make sure the hide you choose seems too small. It sounds odd, but Balls love to squish into the smallest spaces they can. The hide should touch the snake on all sides when the snake is inside, otherwise it's too big. Some of my bigger guys wear their hides like a hat, but it's what makes them happy.

I think your substrate is okay, I've never heard of it being used for snakes, but I don't think it's harmful.

I don't recommend feeding a large rat to any Ball, no matter how big it is. Most Balls will do fine on one small/medium rat once a week. Larger prey items seem to contribute to more feeding refusals and erratic growth. Lots of big breeders stick with small/medium rats, so you know it works. Switching from live to F/T can be tricky. Your best bet is to change setups as soon as you can, don't feed yet. Once your new setups are ready and the snakes have been moved, wait 1 week before offering food. Thaw the F/T rat completely, I set mine out about 4 hours at room temperature, then I run them under hot water for a minute or two, dry them with a towel, then use a hairdryer to get them nice and dry and warm. Just before offering the rat, use the hairdryer to heat the head for about 30 seconds.

They may refuse to eat. If they do, wait 1 week before trying again. Don't worry about them going without food for a while it won't hurt them at all, and will make them more likely to take F/T for you.

I wish you all the best.

Gale