It isn't a fad sport.
1. I would say most countries.
2. Not sure, but it's not like that could never exist.
3. Doesn't matter, all that matters is that it is worthy of being the Olympics, and that it is better than both boxing, and wrestling.
All we have is your opinion. Some would say that tug of war is better than say the high jump. Some would say NFL football (which is far more popular than MMA) ought to be in there. we already have boxing, TKD and (at least at one time) two forms of wrestling. There are far more sports far more popular than MMA that are not in the olympics. Squash for example which has 120 NGBs and has been around for more than 100 years and whose greatest champion-Jahingir Khan was (according to many informed sources) arguably the greatest athlete in history when it comes to endurance and stamina (his heart rate recovery was superior to Britain's two greatest distance runners)
Jahangir Khan, The Legend of Squash- Trond Varlid
IPSC shooting is not in the olympics
american style trap shooting that has far more competitors than MMA is not in the olympics and it is over 100 years old
tell me what makes something worthy of being in the olympics
here is my criteria
1) it has to have global participation-at least 2/3 of the National Olympic Organizations must have active athletes (yeah that kills stuff like Ski Jumping but I am talking about mainly summer games which are not limited to certain climates like the winter games)
2) it has to have at least 50 years of a recognized world championship run by a world governing body that again is recognized by at least 2/3s of the national olympic committees.
3) the competition should mainly be individual in nature with objective scoring criteria.
4) it should not be a duplication of skills (this is an olympic rule that was ignored for beach volleyball-the bikinis sell too many tickets)
Using that object criteria stuff like synchronized swimming, rythm gymnastics, and equestrian should all be dropped.
The sports that meet this criteria include
Athletics (track and field)
swimming and diving
boxing,
Table tennis, tennis, squash and badminton
rifle, pistol, skeet and trap shooting. Double trap would not
archery
boxing
wrestling
volleyball
basketball
cycling track and road-not "mountain biking
Crew and sailing are close calls due to international popularity not being strong
golf
real gymnastics-again the world popularity is dubious since south america and africa have almost no gymnastics
fencing-close call-world popularity is dubious
I had a long day, I will return later this week on this
but the bottom line is that athletes should not be pawns of "causes"