Ok YLL, here are some answers

1)The Quarter Horse got its name for being the fastest running the 1/4 mile races.
2)I think your Jack is a Quarter Horse/Morgan cross(two of my favorite breeds)
3)I think the Quarter Horse is the most popular breed in the world, I would have to look up the numbers
4)One wild horse is the Mustang(like Spirit)
5)I'm pretty sure Kentucky is the horse capital of the world, aren't you planning a trip there to the Kentucky Horse Park?

The photo looks like a Saddlebred or Standardbred but I always get the two confused! Is it one of those two?
(unless it is the Missouri Fox Trotter since the photo is from Missouri.)