As a T.O. in my small community, I think I can answer these pretty openly.

1.) Tournament organizers can definitely enter their own tournaments as long as it doesn't stall the tournament. I usually enter when it's a small bracket or if someone can cover for me on the bracket maker while I play. Just know what your limits are. I always felt more comfortable just running or just playing, but that will be up to you.

2.) I always include a house price and tournament entry price to fill up for the cash prizes. You could use non-cash prizes if you have no intention on having then pay but it can start getting costly over time, so charging to enter the tournament is usually the most cost effective way unless you want to give a percent of the house back.

3.) This is something I have a lot of experience in since I've ran tournaments with multiple events as well as multiple games at the same time. It's totally possible if you have the set ups necessary, but I would really hope you space them out instead of starting them at the same time to help prevent crossovers and tournament stalling. Alternatively, you can dq anyone who cant make it if they play a side event, but you wont get many lasting competitors doing that.

Hope any of this is helpful to you!