Hi Kelly,
The alopecia, weak pulse, and associated itch suggest Blood deficiency
The shifting forelimb lameness suggests a neck chiropractic issue. Is there anyone around who can assess that for you? Even a human chiropractor might be game if you could be there to guide them around the anatomy.
When treating both those things together, if the pulse had been more superficial and toned, I would have suggested Limber Up (Nat Path) or some form of Du Huo Ji Sheng Tang (on which it's based). With no toned pulse, I'd be tempted to start with Bu Gan Tang (NPHC, Kan)
If using granules, I'd probably give 3 or 4 tsp of either one twice daily, assuming the horse is about 1,000 lbs
Let us know how it goes!
Steve