Thanks for pointing these out. It's super helpful, as there aren't enough hours in the day for QA!
1. This is a confirmed bug that will be fixed soon. Unfortunately, there isn't a good temporary fix without significant template edits. You can very well hide the .uix_breadCrumb_toggleList, but that will also hide any other list items in the toggle list. Also you'll want to use the @uix_sidebarMaxResponsiveWidth style property as your media query breakpoint.
2. This is also a confirmed bug that has to deal with poorly defined tab and tab panels in the uix_offCanvasSidebarVisitorTabs template. This fix requires two edits.
3. It's important to note that z-indexing changes depending on the panel animation type. For which animation type are you speaking: reveal, push, or cover?