Back to your question about stopping before you run...
I personally wouldn't do that, what I always did was I would lope a circle and then run.
It's easier on their joints and can give you better run times.
What you do to get them to not rush into running barrels, is to not run them every time. Then they won't associate seeing the barrels as "Oh my god! I have to run."
And with spurs, it isn't good or bad.
I only used spurs on my horse when we were timed. Some horses just need that extra lift that spurs provide to go fast.
"Doing what you like is freedom, liking what you do is happiness."