Can tmj and tight muscles cause your eustachian tube to be jammed open, causing muffed sound when speak ?

Close knit group: Yes, absolutely! the tmj, temporomandibular joint, is in very close proximity to the inner ear and eustachian tube. Only a thin wall of bone seperate the two processes. So any pressure put on the TMJ from tight muscles will in turn put pressure on the inner ear and eustachian tube causing the stuffy ear.

Closed not open: The TMJ can put pressure on the eustachian tube making it feel as if there is something inside.

Possibly: The area around the TMJ complex is pretty compact, so any inflammation in that area could be referred to the ear canal. Pressure from the fluid could cause the muffled hearing that you are experiencing. It is not a guarantee that this is the cause, but most certainly shouldn't be ruled out.

Yes: The same nerve that controls the jaw muscles, also controls one of the muscles that forms the eustacian tube. Hyperactivity of the jaw muscles may lead to hyperactivity of this muscle as well leading to a eustacian tube dysfunction.

Yes: Yes, TMJ can cause ear symptoms. But you also might have ETD. See an ENT doc.