I would try to support him in his decision and do everything possible to keep the lines of communication open. I’d pay for the cell phone so I had some way of reaching him as well as seeing who he was in touch with. Your can help him do this in an adult way as well as manage your downside and his safety by staying involved. There are so many scenarios in which you really wouldn’t want him mucking this out without, at the very least, a sounding board.
It sounds like he opened up to you a bit over the break. Perhaps he wanted to tell you about this plan but felt pushed to shift the conversational gears to a transfer. It sounds like he hasn’t wanted to disappoint you along the way and is now just imploding. Keep listening and loving.