Hi Tracey,
I like your thinking. As long as the pulse has tone and force to it, there is vasoconstriction and the need to move circulation outwards. The dry coat, deep sleep, and chilliness are consistent with that impression as well.
The rapid pulse suggests a need to cool as well, and the coprophagy a possible digestive problem to be cognizant of.
There are probably many options here:
XCHT plus Xue Yu Tang - this has an affinity for the tumor location, is anti-cancer, and is useful for chronic non-healing lesions like acral lick dermatitis
Xian Fang Huo Ming Yin - also excellent for appendicular tumors in dogs with a suggestion of Damp Heat, blood stasis, and non-healing wounds.
Si Miao San plus Dang Gui - more of a general play that acknowledges the digestive aspect; still significant anti-cancer activities. Can be used with Si Miao San.
I'd probably try two or three:
XCHT plus XYT plus SMS
SMS plus XFHMY plus XCHT
Normally we like to be elegant, but in cancer management, you sometimes score extra points for using a large number of herbs that are all really well coordinated.
Hopefully that gets you started. Whatever your gut says about the above....
Steve