Were the two tumors in our client’s dog [name withheld], a consequence of him wanting to heal his onboard human spirit attachments by taking on their discord, causing adverse health consequences for him?

This indeed is the case, and this you were shown during your Protocol work. This is something that does happen and can be a serious problem for the companion animals. As your work has shown you, companion animals have a high frequency of spirit attachments, particularly human lost souls, as their life mission is to rescue humans. This is typically in the range of 75% of all such animals, so it is common for them to have attachments.