Is there anywhere to sit in the general admission section?

Sometimes they will have a few tables out on the main level. Otherwise you can sit on the small ledges that they have on either side of the stairs. That's about it.

There is seating at most shows for about 30 people. These are generally snapped up by the first few people to enter.

It depends on the show. Usually if it is a sold out show there will be no seating. If it is a smaller show there will be seating but it is first come first serve

No. You can only stand in the general admission.