I think your husband and you need to upgrade your firmware.
Your shelf problem sounds like one I saw when creating a new shelf. Once you enter the name of the shelf and press the next button, it would take a while to get to the screen to select books. How long it took depended on the number of shelves and number of books. I never saw it hang completely, but I don't usually have as many books on my readers as you have. Opening an empty shelf had the same delay as it also went to the add books to shelf screen. This fixed in either the 2.4.x or 2.5.x firmware.
Your husband's problem with font size is a 2.3.x problem. The font size would get tiny when going from one chapter to another in an epub. This was definitely fixed in 2.4.0. Actually, it might have been in 2.3.1 and fixed in 2.3.2.