All browsers do not support All fonts, and there is nothing you can do about that (that I know of). The only way I know to have unsupported fonts appear anywhere is to convert the text into an image.
As far as your remark about navigation shifting, do you mean the transition from the menu bar to the Mobile menu?
If so, this is based on screen resolution, and some Ipad have the screen resolution of a desktop, so it may not transition to the mobile menu on them. Given you have “Plus” you can use the Smart menus and experiment with raising the threshold for the Mobile menu (both otptions are at the top of the MAin Options > Menu page). The default transition resolution is 768px, I think if you raise that just a bit, you should be able to make the mobile menu appear on Ipad.