Convert regular account to a child account OR set time limits on regular account

I let my son use my Microsoft account for many years and he's accumulated a number of games, items, etc. on Xbox mostly. However, I have to be able to set time limits for him and we can't figure out how to import all of the items we've purchased to his child account. The other alternative is to set up time limits on the administrator account but there does not seem to be a way to do that either.

How can I transfer his purchases to his child account from the admin account?

Is there a way to set up time limits for Xbox for the admin account?

Thanks for any help.

ABS

:)