Can TMJ radiate to the shoulder & back?

Yes. Temporomandibular joint dysfunction syndrome (TMJ) can cause muscular spasm type pain which can radiate and/or extend to the neck, shoulders and upper back.
Absolutely. Tmj is one aspect of a general group of craniomandibular disorders. Postural changes that can influence each other from the top of your head to the bottom of your feet. If your posture is not centered, the torsional changes cause nerves that go to your shoulder and arms to be "pinched.". One goal of its treatment, is to align the head and jaw. That often relieves these types of symptoms.
Yes. Yes, usually the TMJ is painful and also neck pain. Would be unusual to have TMJ pain and shoulder pain without neck involvement.
It's possible. It is possible that the pain caused by your TMJ is causing other muscles in proximity to also tense up, leading to pain. All parts of our body are connected; nothing works in isolation. Try motrin, stretching, stress relief .