they define insanity as an inability to accept reality. Can you get him committed?

My parents seriously looked into it, but it doesn't look like he meets the legal standards to allow him to be committed involuntarily.

but enough for me to be worried

If you are concerned, then I would suggest that you say something sooner rather than later. My brother was an extremely high functioning alcoholic, right up until his body collapsed on him. If you suspect there's a potential issue, talk about it before it can cause permanent damage.