Hi Brett! If you would describe the horse as Hot (red tongue, tachycardia) and Deficient (thin pulse, response to tonification), then I would be wondering about an Empty Fire formula to get the Shao Yin organs in alignment. How about Zhi Bai Di Huang Wan?
If he's not that tachycardic, then maybe Tian Wang Bu Xin Dan?
If you get the sense he's more Damp (and not tachycardic), then I would go with BWDHW
Hopefully that somehow helps you out! Hopefully you can keep tabs on him and see how he does, and get back to us!
Steve