There used to be an EU-centric fighting tournament called Fight Club or something like that which happened on... Fridays? I forget exactly when but they held it out in Costa. I don't know if it's still going, but it might be worth checking into!
As for the questions, let's see here...
1.) A lot of the basic rules that are in the events that happen right now are there because they're pretty solid rules, so using existing tournaments for basic rule ideas definitely can't hurt. For example: Grindstone's no-killing rule and the Runestone/Spellguard's defensive systems that "absorb" spells to basically do the same. So, having that sort of rule in place is kind of a given, unless you're wanting to run a more gritty "no holds barred" tournament - which has its own drawbacks since I'm sure many of the participants would expect to be the ones doing the killing and would react poorly to being the ones being killed.
2.) You can come up with your own combat rules, but the GS ones are used as much as they are because they're exactly what you're looking for in Question 1 in regards to all the other rules: quick and easy to understand. Two people roll, highest roll wins, reroll on tie. Leaves it all basically up to RNG with (little to) no way to really game the system, which could happen with a different rule set.
3.) I think one of the big things about running the event is building trust from the audience you're running it for. That way they're willing to acquiesce to having you (and whatever additional staff you have) "in charge" for the duration of the event. Doing things like being on time, being polite and courteous to the participants when they're behaving, and being firm but fair when they're not. Things like that.
That's what comes immediately to mind. I'm sure others will chime in with their own thoughts. Overall, I'm of a mind that you should just keep it simple, keep it approachable, and keep it fair. That way you'll keep it open to the widest number of people.
As for the questions, let's see here...
1.) A lot of the basic rules that are in the events that happen right now are there because they're pretty solid rules, so using existing tournaments for basic rule ideas definitely can't hurt. For example: Grindstone's no-killing rule and the Runestone/Spellguard's defensive systems that "absorb" spells to basically do the same. So, having that sort of rule in place is kind of a given, unless you're wanting to run a more gritty "no holds barred" tournament - which has its own drawbacks since I'm sure many of the participants would expect to be the ones doing the killing and would react poorly to being the ones being killed.
2.) You can come up with your own combat rules, but the GS ones are used as much as they are because they're exactly what you're looking for in Question 1 in regards to all the other rules: quick and easy to understand. Two people roll, highest roll wins, reroll on tie. Leaves it all basically up to RNG with (little to) no way to really game the system, which could happen with a different rule set.
3.) I think one of the big things about running the event is building trust from the audience you're running it for. That way they're willing to acquiesce to having you (and whatever additional staff you have) "in charge" for the duration of the event. Doing things like being on time, being polite and courteous to the participants when they're behaving, and being firm but fair when they're not. Things like that.
That's what comes immediately to mind. I'm sure others will chime in with their own thoughts. Overall, I'm of a mind that you should just keep it simple, keep it approachable, and keep it fair. That way you'll keep it open to the widest number of people.