Tooth #19 root abscess; extracted and bone graft. Two months later swollen lymph nodes and hard lump angle of jaw. On clindamycin. Did abscess spread?

Hard lumps. It is really hard to tell where your infection may be coming from, but among the list of possibilities is that your body rejected the bone graft, there may be another tooth along your bottom jaw infected, your gums may be infected, you may have an infection elsewhere in your head, or the lumps are not infection. Best to see your dentist to give definitive answers. I hope the best for you.
Possibly. But for a definitive answer, you should call the dentist or surgeon who did the bone graft. They can examine you and take a radiograph of the graft site.