Sumo

The wins/losses listed are for the tournament. There are 15 days and everyone has 1 match per day (at the top two divisions. Below that there are only 7 matches).

Does the Shinto guy (priest?) have a role like an umpire or referee?

Like the guy standing in the ring with the two wrestlers? That's the gyoji, who is the ref for the match. He shouts instructions and information to the wrestlers, like telling them to put their hands down at the beginning and calling out during the match to tell them that it's still live and no one has yet lost. He also determines the winner of the match, though if one of the five (along with two others watching from the replay booth) ringside judges, or shimpan, thinks they saw something that would run counter to the call from the gyoji he can call for a discussion where everyone meets in the ring and they talk about who should win.

Are wrestlers generally expected to only use traditional techniques? There doesn’t seem to be that much variety in technique.

There are 82 winning techniques, called kimarite, recognized by the sumo association, along with 5 more that are winning non-techniques (such as when a wrestler accidentally steps out of the ring without his opponent attacking). You tend to see the same ones over and over because some are simply easier to do than others. It's much easier to grab a belt and push or smack someone repeatedly until they're out of the ring than it is to pick someone up and throw them behind you. Here's a brief stylized video promoting a HS tournament that shows a very quick rundown of the techniques, but there are more detailed vids of course.

Is (western style) sportsmanship not practiced in Sumo

You do see wrestlers sometimes catch their opponents after they've been pushed out to prevent them from falling off the ring, but I think you don't see them usually offering a hand up from the ground because if they're ok they don't really need help getting up, and if they're hurt they don't want to exacerbate any injury.