1) How much you spend on entertainment is irrelevant. My point is that most people who gamble see gambling as entertainment and are willing to pay for it as such. The fact that people become addicted to gambling says more about the people themselves than it does about the activity. There are twelve-step programs for for people addicted to alcohol, shopping, sex, and almost anything else you can think of. Does this mean sex is evil, of course not. You seem to be trying to conflate the problem of gambling addiction to the activity itself.
2) As with many things, I'd venture to say you could chart gambling winners and losers as a bell curve with those winning or losing a small amount being the most numerous and those winning or losing a large amount on the ends of the curve. Without getting into the semantics of the term "many," of the millions upon millions who go to Vegas the number of people who "win big" would be a fairly high number, even though the percentage would be small.
3) You need to understand that the casinos do not care about how much any individual wins or loses. Again, this is because the odds are in their favor. If 100 people sit down at a blackjack table, odds are there will be a person or two who will win a large amount. There will also be a person or two who will lose an equally large amount. The casinos know and expect this. In the long run, regardless of how any one person fares, the casinos will take their cut.