Welcome back! 
- I don’t think the size of the toast can be adjusted. Maybe by increasing the font size of the main text (the item being quizzed), it can be made big enough to avoid being covered by the toast. Though in my experience, tweaking the font sizes can break the UI. (Esthetically, not to the point of being unusable.)
- I think this is a no, too. You can use self study, and only select burned items, but that won’t keep track of the progress. You might find some ideas in this thread.