Not necessarily. Conduction block cannot be discerned on many MMN patients, including me. Some official diagnostic checklists don't even require conduction block anymore.

While MMN is typically motor rather than sensory, there can be some sensory involvement. I have developed some numbness after five or 10 years.

While your symptoms don't sound that much like MMN, individual cases vary quite a lot. Weakness can be subtle at first; I initially noticed it when I had trouble tearing open oatmeal packets. Nobody took it seriously until years later when I woke up with sudden loss of thumb extension, followed by three more fingers over the course of eight months.

Unfortunately, there is no definite diagnostic test for either MMN or ALS. One thing that helps distinguish them, though, is upper bulbar involvement. My Mayo Clinic neurologist told me that diagnosing MMN is more of an art than a science. On my first mayo visit I had five solid days of testing, mostly to rule out other things like heavy metals, B12 deficiency and Lyme disease.We have many people in our online groups who have bounced back and forth between MMN and ALS diagnoses, and some who still don't know which they have. While treatment with IVIg can be of diagnostic help, 30% of MMN cases do not respond (including me), and some ALS patients do respond initially to treatment. So even that is not definitive.

There is a whole alphabet soup of common, to uncommon, to incredibly rare neuropathies. Again unfortunately, the average time to diagnosis is 7 to 10 years.

You sound pretty knowledgeable, so perhaps you have a head start. My advice is to see more than one neurologist experienced with rare neuropathies.