Yes all of those are pretty great Cow horses. Leo was technically a racer, but his offspring were big cow horses. Jet Deck was a racer too. The others were famous cow horses and halter horses. They also are responsible for a lot of the great reiners out there too.
Line breeding is good because then you have a lot of the powerful lines. Most of the time it works, but when it doesn't then it's inbreeding, but I'm pretty sure it worked and it's far enough back now that you're boy is fine.