If he is out during the day, he is stressed. Move him back to a tub.
Every time you introduce the snake to a new enclosure, it will test the boundaries of the enclosure and roam and look for a way out for up to 3 weeks. Putting him into a 20g probably didn't help. Moving him to a smaller enclosure with two tight fitting hides will probably help get him back on a good eating schedule.
If you are handling this snake, stop. Handling them will stress them out. They are not "happy" to come out nor do they "love" being handled. Being handled by a giant monster is stressful to them. Some are much more sensitive than others when it comes to stressful situations. If yours is shy like you said, handling will do more harm than good and sitting out on a piece of wood in the middle of the day means he doesn't feel safe enough to sleep in his hides.