Hi Amy,
Tough case. The vital clue might lie in the wholly unexpected response to the BXBZTMT and TMGTY. Both descend, the former is drying. So the dog might have a cryptic need for increased cerebral blood flow, not decreased.
Using such a formula would increase cutaneous blood flow as well. That's okay, but it would need to be anti-itch. Probably the formula that best matches this criteria is Qing Ying Tang (Clear the Nutritive Decoction).
I guess the only other thing to be sure of is that GB points don't correct the pulse. If you know where GB 34 is on the hind leg, you could try massaging it or needling it. If it markedly improved the pulse, then we need to be looking at formulas related to Minor Bupleurum. In this case, the TMGTY would have been aggravating by 'pressurizing' the system through its descending action, when actually what was needed was a mixed raising and descending action that opens the Triple Burner, allows Qi to be formed, and Yang to descend. So get the dog back in and check that out. If GB 34 or any other GB point help, then a formula to address both the neurological complaints and the itch might be Chai Hu Jia Long Gu Mu Li Tang.
Hopefully you have some success here.
Good luck,
Steve