Sounds like you're on the right track. At the size he is currently, I would consider moving him to a 15qt tub with two hides and a waterbowl. While these snakes live in the wild, and we sometimes think "big open spaces out in the wild", BP's usually take up home in old termite mounds or small animal burrows. They like and thrive in very small, tight quarters. The are most comfortable in hides they can barely fit in... when they feel security from the sides and top of the hides against their skin.

If your bp is staying his hide all the time, that means he likes it there. His needs are being met, and he's happy. If he was out and moving around all day long, that would actually be a bad sign. I'm sure if you sat up all night, with little or no lights on, you'd see he comes out of that hide and is checking things out. It's likely the extra empty space in that larger tub does frighten him a little, so he's less likely to come out and explore. You may also find that moving him to a smaller tub will help his feeding as well. Experienced snake keepers will tell you that if they have a snake that is refusing food, one of the most common things that can be done is to put them into a smaller container. Again, the more safe and comfortable the snake feels, the more likely it is to eat.

Being young, if he doesn't eat regularly, he'll likely lose some weight. At 128g, he's about ready to go to f/t rat fuzzies or medium mice, I'd say. Something around 15-20g. Thawing out the frozen in a ziplog bag is correct. i do that until the prey feels soft and not cold. Then I refill the bowl with the hottest tapwater possible, and let the bag soak in that for about 5 minutes. This will really raise the temperature of the prey. I remove the bag from the hot water and immediately remove the prey and offer it to the snake. Some people will use a hair-dryer during this step to really heat up the mouse. You're snake will sense that heat signature and smell that yummy rodent, and BAM!!