I could be reading my own story. Very, very similar. I was seen at Mayo in May (ha! always laugh at that) and they diagnosed my Dysautonomia and left leg neuropathy, and pelvic dyssenergy. I already had diagnoses from my local specialists of Gastroparesis and esophageal dysmotility. All being idiopathic, as in they have no idea why it's happening. All symptoms of something "bigger" as my drs say. Since mid Sept, I lost 20+lbs, and very similar weakness issues as you described. I still work full time, but every day gets harder. I'm couch-bound today and have to trek via train, subway and walking to get to my Neuro appointment tomorrow for my EMG and if that's normal, a skin punch biopsy to look for Small Fiber Neuropathy (I saw someone else refer). I've had all your same testing except a lumbar puncture. When they ruled out MS, they stopped after the initial EMG and MRI as they were normal. LEMS diagnosis was ruled out for me, but they'd wait until your Paraneoplastic panel comes back before probably confirming that. I tested negative for that marker.

Like you, I've had very compassionate doctors, especially my current Neuro whom is doing everything she can to find out what's going on. Every day, I notice more muscles that are newly fatigued and now have twitching and Charlie horse-like cramps in all my extremities. Typing is painful now too just over the last few dats. It's scary, so I can absolutely 100% empathize with you. I'm also a nurse with experience in evidence-based research, so it's a blessing and a huge curse at times trying to look up latest research, however, the Neuro has encouraged me to help HER find something, so it's almost like another job. A Dr. House like job lol.

Here's how I see it, and I've only come to recently embrace my thought process. Whatever is going on, I know my doctors are doing everything they can to find out what's going on. I'm going into the city to essentially rule out the worst of the worst diagnoses, one being ALS, another Myasthenia Gravis. The rapid progression of symptoms is terrifying, but all I can do is keep going. Unfortunately, my current status, is just my new normal. If my testing tomorrow is normal, I'm going to apply for the NIH Undiagnosed Disease program with my dr's help. Funding just got cut though, so who knows how long it will be around. They keep your genetic profile if even they can't find out what's wrong and if they ever diagnose a new disease or find a biomarker, if you match...you can see where I'm going.

Anyway, in the end, so long as I know we, as in me, my family and my doctors, who are all amazing, did everything we can to get to the bottom of all this, I'll be okay. It's awful, I know. I wish you the absolute best. I really do. For now, keep your mind busy; binge TV, movies, read...I have 2 kids, 9 and 7, so they keep me entertained. My husband is also my third child. We have fun, even if I'm on the couch or stuck in bed.

By the way, you said you live in Alaska. I never had a real bucket list until a few months ago, but the northern lights are top 3. Even if I'm in a wheelchair, I'll get there 🙂 Also, there's a homeopathic clinic in Switzerland known for their ability to help "reboot" your system. Worth a shot if I'm still an anomaly.
Good luck, best wishes, stay hopeful and positive, and happy holidays!
Alli