Hi Juan,
I read your whole post with great interest.
I don't know what were your previous EMG findings and which muscles were checked. You mentioned you had a clean EMG. Was that also in the tongue, bulbar area?
Do you have tongue weakness? Slurred speech? Difficulty swallowing?
Did the neuro check your jaw reflex?
Regarding the thenar muscle reactions when hit by the hammer it happened to me a few times too. When hit hard the muscle twitched a few times.
Brisk reflexes in both sides could be also due to stress... If you go to another neuro just try to take a benzo a few hours before so you are more relaxed. This worked for me.
When are you planning to make all those tests? Keep us updated.
Regards and all the best