In that she isn't unique, that is what most powerful mortals do.
Yes, but not through indirect means of enforcement, through direct application to the subject. Mab doesnt have to send someone for you, you deliver yourself to her. For someone like Nameless that must be galling.
Harry himself was interested that going past a threshold without invitation not only removed the greater part of his power but also the grip of Winter Law. And yet, he wasn’t paralysed and he still had the physical conditioning the Mantle had left him with, a 6 foot 9 inch man as strong as humanly possible.
Harry could theoretically ask the Carpenters to revoke their invitation (Charity could do it genuinely) and once inside past the strongest of all thresholds make all sorts of plans Mab won’t know about in complete violation of Winter Law, which hinge on him being continuing to appear to be bound by Winter Law. That I think is coming, a time Harry needs to disobey Mab because he is right and she is wrong.