I would like to mention that the large block of text was rather hard to read and comprehend. You may not have been able to see it all on your mobile, but next time, would you please try to use more paragraphs? Thanks
Anyway, from what I understand, I am willing to bet that a lot of her problems with spookiness and freshness is due to her getting too much feed and not nearly enough work.
Am I correct in assuming that she has been getting grain (except for the past few days) while being turned out? Does she need it for any special reason? Is she hard to keep weight on, etc? What kind of grain is it?
I think what would probably help her more than anything is less grain (none at all if she will maintain her weight without it) and more work (at least 2-3 times a week, give her a ride like you did today). To me, she sounds almost like an angel to behave as well as she did for only being ridden twice this year and getting grained.
As for the treats, so long as she doesn't start to get nippy, IMHO, you can feed as many as you want. If they are high in sugar, I would try not to feed them too often as too much sugar is unhealthy, but I really don't think it will create a problem with her training.