How did the young man take his turn? (spoilers) The sequence of events:


The old man pots the two balls
The younger man attacks him just as they are potted
The old man dies (or is knocked out or something) in the fight
Young man returns to the table and proceeds to pot the rest of his balls


After the old man pots the balls, surely it's still his turn as he scored? Or did the rules of billiards that they were using not necessarily have turns? Or maybe he used the old man's body and made him miss?

Is there any proper answer to this, or is this just a big plot hole that was skipped over?
Sure it was the old man's turn... except he was incapacitated at the time, so he couldn't do anything, which is why the bartender allowed the young man to continue the game. In a normal game of billiards, if a player is knocked out and no one is able to substitute for them, then the game would naturally end. In Death Billiards, however, ending the game was not an option, so the young man decided to take over the old man's turn and finish the game