Wow... Those are some serious questions. I think you are on to something though, but at the same time, could it be, that deep down, a man that in a less "civilised" era would without question be one of the tribe's warriors, simply just enjoys measuring himself (ooh er) against others? I mean, why on Earth would you willingly and with a smile on your face step into a boxing ring? Is it possible that some of us (myself included) find a sense of worth in the extent in which we can assert our physical dominance over others?
I'm currently writing my dissertation on risk taking behavior being an evolutionarily adaptive method of mate attraction.
Unfortunately for me, this means I have to read a ridiculous amount of evolutionary theory surrounding risk taking, aggression, sexual dimorphism and intrasexual competition. Let alone other topics such as the biology behind the whole lot.
Long story short, there are many benefits to taking risks, being aggressive and physically dominant over others in an ancestral environment - you'll have (in theory) more success in hunting, defending both territory and family and a higher status within social groups, meaning the women will be flocking to get a piece of you (since you're going to a be a great provider for them and future children).
Funnily enough these characteristics are directly linked with high amounts of testosterone (being more 'manly'), leading you to be larger and more aggressive - something which also requires a very strong immune system. It's theorised that these behaviors are all an honest display of a well adapted immune system, and therefore an honest indicator of 'good genes'. Aggressive behavior serves the dual purpose of gaining resources and attracting a mate by effectively 'showing off'.
So, really, there is quite a lot of truth in what you wrote. You're just fulfilling every role that need to in order to survive and have a relatively good reproductive success - which, in evolutionary theory, are the only two motivators worth mentioning.
Bugger, that was quite long actually. Sorry.