Macs
I will continue as the devil's advocate. There may be 2 problems. Firstly there is the problem of getting his money out. That is paramount. You have to ensure that he can get his money out now and in the future. The second is another elephant. That this does not control him. When I was young gambling could have controlled me except that I got taught a lesson very early after leaving the local game with my winnings.

Going up in stakes is going be a different game with a diferent type of people.

I suggest that he works out a comfortable bank to start with each session and pull everything else off the table each day.