How long does masseter Botox take to attach to the nerve therefore stopping further risk of migration?

Your photos are helpful to see your masseters. I would be careful of treating only the TMJ since it could cause less structure in the lower face. If the TMJ causes you pain, I would treat it, but consider a filler/hylaronic acid to fill in the "sulcus" or area around chin. Hope this helped.

Yes, you can have Botox and fillers a day apart. However since you mentioned that the Botox treatment has caused significant changes to the jawline you could consider waiting two weeks for your filler session. At that time your Botox will be in full effect.

Please watch the video below for a detailed answer on how Botox is used safely to treat symptoms of TMJ (Temporo-Mandibular Joint) Disorder