Ringmaster

This doesn't have anything to do with the character of the Ringmaster, but I was intrigued to find out who played the part. It was George de la Pena, who used to be a dancer with American Ballet Theater back in the 1970s, and then played Nijinksy in Herbert Ross's 1980 film. (Just a little trivia...)

I don't think the ringmaster is a personification of death. I think he might be more of an embodiment of the emotions that go along with death. Notice that when the children are content in their limbo (such as at the ball), the ringmaster is represented as menacing. When Ryan is ready to make the leap, the ringmaster is almost comforting.
The hockey scene I see as a representation of Ryan having to break Melanie out of her complacency. Her dawdling, if you will. Her denial and lack of faith is what brings them to the hockey rink. Note that after the hockey scene, her character acquires much more dimension. She is more willing to accept the idea of making the leap, which is after all a leap of faith.

That's my take on it anyway. A wise film maker once said it was his job to provide questions; it was the audiences' job to provide answers.

By the way, I think it's the trapeze guy that is supposed to be death.

The Ringmaster, as you call him, is more of "The Gambler". You see a lot of movies or storys, where the Gambler is a personification of Death. You gamble for your life as bait.

We all know the storys about gambling with Death for eternal life - but what will the price be? Your soul, your youth? It's always about the impossibility to cheat life and Death as an inevability. Still, every man wishes for eternal life at some point or another.

If you want a perfect comparison to this theme, go watch 'The Imaginarium of Doctor Parnassus' (2009).

Good ancient storys on this theme would be 'Orpheus and Euridike', 'Aeneasium (Aeaneas Travels)' or 'Gilgamesh'.