Man, you are only shooting about 40# of draw weight! I don't think you will weaken the 5575s enough with 250 grains up front to cure your problem, especially with arrows already cut to 29". I think you need to bite the bullet and get the right shafts. Some bows are forgiving enough of spine to let you get by with it, but yours is obviously not.
By the way, if you are bare shaft tuning, don't worry about the direction of the nock, just the impact point. The goal is for your bare shafts and your fletched shafts to group in the same area. If you are off the target at 15 yards, that's a lot. I start at about 10 yards and work back to 20 or more, but you have to have shafts spined closer to your draw weight (not what's printed on the bow, but what YOU draw).
I shoot Beman ICS Bowhunter 500 shafts cut to 29 1/2" with 235 grains up front from my 46# Kanati and they fly like darts, but I draw 28". These shafts are also MUCH weaker than the ones you are trying to use, plus my Kanati is very forgiving.
I think you need to start with 600 spine shafts and work with them until you have them the length you want with the FOC you want. You might get by with 500s, but you will need quite a bit of weight up front unless you don't mind leaving them full length.
Hope this helps.
Russ