How big a problem is sports betting and other gambling to the health of the force?

I don't think it's the gambling that is the root cause of the problem, it's a behavioral issue. It could just as easily be drugs or alcohol. They are looking for a "high", and gambling can provide that. I would guess that there are also many soldiers that spend all of their money in bars and are broke for the rest of the month.
I am a gambler (on horses) but it is a hobby of mine. I only play when I can afford to and I see an opportunity where I can put the odds in my favor. It's takes many hours of work to do this, but it's one of the few games out there where it is a possibility. All of the other games are stacked against you.
In theory, I could take a problem gambler and teach them how to win, and so by most people's standards, he/she would no longer have a gambling problem. In reality this wouldn't work because they are playing for a different reason than I am, and would never put the work into it that winning consistently requires. They are compulsive and just looking for that "high".
I wish you luck sir, and I hope that you can help them.

Gambling like most vices isn't a problem if done responsibility and in moderation. It is when the individual takes it to excess that it becomes a problem. In my time in the Army, I only ran across a handful with this problem and it destroyed their families as a result. I have seen Soldiers sell plasma to buy beer, and I may have done it once or twice as a young Private lol.

So outlaw sports betting......then what.....a gambler (someone with a true problem) will find something to bet on. The issue is not "Sports Gambling" it's people who exhibit the addictive behavior an gambler. We need to put as much effort into educating people one the dangers of this as we do alcohol consumption. Again the problem is not gambling or alcohol.....it's the addictive behavior exhibited by the addicts. Just my two cents.