I agree with the above - you should get a physio assessment.

The periodic muscle spasms are compensations for something else during your walking - the most obvious culprit as you say is the big toe however it may not be...for example why is your big toe the only joint with arthritis?? Perhaps there is something else causing you to put pressure on the big toe in a certain way that is causing the inflammation in the joint...

Find someone who can check your pelvis and thorax as it seems someone has looked at your feet and neck. My bet is that either your ribs or lumbopelvic region is dysfunctional... the trick is finding out which is the key driver of all the different dysfunctions you have - that is, when you address the key driving force, all the other dysfunctions improve.

Good luck!