My thoughts are...
1st. Don't buy a seigework's product, but you already did, so let's work with what you have,
2nd. ALMOST everyone measures tiller by looking at the "deepest part of the upper limb and lower limb," but that is incorrect. What you are looking for is the point where the limb goes from the working section to the non-working riser. By "riser" I do NOT mean the center block of wood the riser is milled from. Instead, I am referring to ALL OF the non-working portion of the bow. You have to measure from where the limb STARTS to work...hence..."FADEOUT." This is where the "riser" (non-working part of the bow) fades out to the limb (the working part of the bow). Some bows don't have a "deep part" for example...
And, MANY BOWS have a "deep part" in the riser that is a non-working section) of the bow and has nothing to do with tiller or upper limb. Therefore this is isn't where you properly measure either. For example, if you look at this bow, you can see the "deep spot" on the lower limb is just below the grip and considerably above the fadeout, yet the upper limb doesn't have such a "hallowed" spot on the riser. This bow may "measure" an inch so of different tiller when looking at the "deepest" measurements, but if measured properly from the fadeouts it may measure even to 1/4" (depending on the design of bow and shooter)...
The proper way to measure tiller is to measure at the fadeouts.
3rd. Make sure your fletching isn't hitting the bow. For the sake of time, try shooting "cock feather in" and see what happens. If it shoots better that way, you need to turn your nocks so you don't have a feather pointed down.
4th. I suspect that if you are already that high, moving 3 under wouldn't help as that would further work the lower limb. HOWEVER, using a stick on arrow rest to raise the arrow might help a lot as that would further work the upper limb...and this is what I believe you need in this situation. Also, I suspect that if you get your hand OFF the grip and only hold the bow by the throat of the grip, that too may help a lot.
5th. I wouldn't change how I shoot to accomidate a poorly crafted bow. I wouldn't sell it either. I would either want a refund, retiller the bow myself, or I would give it away to a kid to use as a yard plinker.
Sorry...but these are my thoughts on the matter.