Don’t forget to use search and if I may say might have been worth asking each distinct question in a separate topic if existing topics had not existed. However there is much existing discussion on each.
The first part of your question is covered here in some detail:
https://mvertigo.org/t/vestibulopathic-gait-youre-better-off-moving-faster/2799?u=turnitaround
(Topic behind User Trust Level threshold: I’ve PM’d you)
I think it’s fair to say this reflects a compromise to the vestibular system and shows that automated mechanisms take over at higher speeds that aren’t as significant at lower speeds.
We’ve had quite a lot of discussion on the involvement of sinuses on here too. Possible middle ear impact? Vicious cycle of that and migraine swelling tissue? Chicken and egg?
Please search on sinus, but see this post as example:
Finally there’s a Women's Biz 
Category with a lot of discussions on the relationship between MAV and menstrual cycle. Again search is your friend.
Let’s not repeat those conversations on this Topic if at all possible and feel free to contribute to those existing discussions on those Topics.