What damage could I have caused by doing gentle massage after SMAS Facelift?

I/m glad it was gentle.  Tissues are trying to stick down to deeper structures during the early period of healing.  If you didn't stir up bleeding or fluid accumulation, you are probably fine.  Follow your doctor's instructions as they have been down this road before.

From the description of your massage, I would say it is very unlikely that you did any damage to your face 5 days after your SMAS facelift.  I would recommend following the instructions of your surgeon in your recovery period to give you the best result though.    

Massage after facial surgery is surgeon preference; while some surgeons do not feel it to be beneficial, I generally recommend 3 lymphatic drainage massage treatments after facelift surgery.  These are gentle as well, and promote lymph fluid drainage and speed the resolution of swelling.  Most deep sutures are quite hardy, and several in number.  It is unlikely that a gentle massage will disturb any of them.  This being said, review your surgeon's instructions and keep a close follow-up with him/ her.  Because each surgeon will have slightly different post-operative instructions, your provider is best able to answer your questions and concerns.  Good luck in your recovery!