Could a prominent(possibly deformed) tailbone and neurological symptoms possibly indicate a tethered spinal cord in an adult?

Tailbone: Prominent tailbone is not directly associated with a tethered cord. Check with pcp or neurologist for nerve symptoms.

Nope.: Tethered cord would only cause symptoms during growth spurt when spine elongates but cord is "tethered" and thus stretched. It would have absolutely zero effect upon your coccyx. When you hear hooves, it's more likely horses not zebras. Get an MRI if neuro problems, and you will likely find nerve pressure from disc or bone spurs. These are treatable nonsurgically in most cases.