Hey!
The lumbar puncture was not the most pleasant way to spend an afternoon, but I also had the delight have having a nerve/muscle biopsy.
Keep your head up, there are so many variations of this disease that you might be on the lucky side and have a very slow progression.
After the procedure you may have a headache, and feel a little stiff, but will feel back to your “normal” within 24-48 hrs!

Keep fighting!

You might want to ask how quickly they get the LP results. My doctor wanted to do it in his office, and I think they told me 1 week for prelim results. I have been told if you go to the ER, results are immediate. I was very worried about the headache and the doctor did not reassure me, so I did not have it done. People told me to lie flat for about 24 hours afterward, and also you can get a blood tap or something like that if you get a leak, where they take blood from your arm to seal the leak.

Sounds like you are on the right track. I am rooting for you to get better treatment/response than I did!