wrote:

I think it's been about a week and he probably feels safe
in that room but he may also want to come out when nobody
is watching.

He's the only cat in the house and I don't know if this is
good for an ex-feral cat that's going to be kept indoor.

I think he can certainly stay in the room for longer than a week. Even with a
non-feral cat, a week wouldn't be very long to keep confined. I'd say keep him
there until he starts to seem more secure, probably another couple weeks
anyway.