I was also surprised when the ENT ordered a hearing test when I saw him after a month of a "plugged" ear. I thought, "I already know I can't hear out of that ear, why do I need a hearing test?"
But the answer to your first question is, YES, the hearing test is absolutely necessary and will help the doctor figure out what's wrong. He needs to know whether you have a CONDUCTIVE hearing loss (a problem in the outer ear or the middle ear) or a SENSORINEURAL (nerve) hearing loss, which would indicate a problem with the inner ear. The hearing test will give him this information. Then he will know how to try to treat your problem.
If the blockage goes away when you tilt your head, it is probably some kind of conductive or Eustachian tube problem, but it is very important to rule out inner-ear problems.
I was shocked when the ENT came in after my hearing test and told me that my ear wasn't just temporarily "plugged"--I had a severe-to-profound nerve (sensorineural) hearing loss, which turned out to be permanent.
If you are not having pain, you probably don't have an infection, so I wouldn't worry about that.
Good luck and I hope your symptoms resolve soon. It sounds like it will turn out to be something treatable, an annoyance rather than a serious threat to your hearing.
My brother in law suddenly lost his hearing in one ear and after tests it was determined that he had suffered a minor stroke
That was the best final theory for my hearing loss as well. It occurred when I sneezed hard, so it could have caused a stroke in the inner ear.