Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
This torn pad can be very painful so giving the Metacam is a good start. I am not sure if this toothache is related and becoming unsteady on H's rear legs may be a separate issue. Because of his age, this could be due to arthritis in his back or hips and the Metacam should help with this also.
There is a chance that there may be a bacteria that has gone systemic and affecting all of these areas. For this reason,if H does not respond well to the Metacam within a day, have your vet examine H and run xrays to know for sure that this treatment is appropriate.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, Dr. Loretta