I think scalps toughen up given time.
When I first started (many years ago) I had itching and used to use scalp protector and would regularly wash my scalp with Neutrogena Itchy Scalp Shampoo.

Both these things really helped.
This is the shampoo:
http://www.instyle.com/instyle/best-beau...16,00.html

BTW, I heard Walkers have brought out an extra strength scalp protector.
I also found tape irritated my scalp and white glues don't.

But these days the only time I get itching is if I leave my detachment too long and the glue seeps from the perimeter in to my natural hair.
Under the piece I have no problems.

So I hope your scalp toughens up in time, but it sounds as if you're taking the right precautions.

PS. I've also been meaning to congratulate you on how well your hair looks. TOTALLY natural.
I know others have suggested you bring the front down and you say now you have.
But don't go too far.
Its the irregularity of its position that makes it look so natural and completely deters detection.