Anyone ever have caffeine withdrawal?

Yes. Typically my withdraw only manifests as all day non-stop headaches (which can be 100% alleviated with a single children's NSAID once a day) although there can be brief periods of extreme fatigue associated.

Waking up with hands asleep could conceivably be related to withdrawal but that seems somewhat doubtful. Likely its psychosomatic especially considering that you're worried about having a brain tumor. Your doc may suspect tumor but in most cases it's such an unlikely disease that he will not recommend testing. The diagnostic procedures for a brain tumor can cost multiple thousands of dollars to assess for a condition that an otherwise healthy young man might have a 1:50,000 or so chance of having. Yes, doctors have to make moral judgment calls - they balance cost, time, and patient suffering with probabilities of a certain condition being the problem. Regardless, the progression or retraction of symptoms will occur over time and generally provide more insight into the cause of the discomforts without substantially increasing your risk of death or serious injury.