Sorry to hear about that, thought it would've gone a lot better for you. Some of the problems you listed have pretty easy solutions though, for the My Computer issue you can open up explorer and at the top click "View", then on the right side of the top menu click on "Options" it'll bring up the old Folder Options from previous OS versions. The first option is there to turn File Explorer into My Computer by changing "Open File Explorer to - Quick Access" to "Open File Explorer to - This PC/My Computer".
Also "Quick Access" is the same Favorites side-bar feature from Win7, just renamed.
As for your mother's issue, if you did a straight upgrade, all her documents and pictures would remain intact and right where she left them. You can have all the main explorer folders listed in the Start Menu as well by going to: "Start > Settings > Personalization > Start > (at the bottom) Choose which folders appear on Start" and there, they can pick all the folders they want to show up there. As for the weather gadget app, you can use an alternative desktop gadget out there called
Rainmeter which is fully customizable with weather, system specs, etc.. tons of skins to download also. Or, there's the Weather app that's already installed.
All the apps can be uninstalled, I don't even use them except for the Photos one and on occasion the News one. What features was he worried about? Pretty much all features since Win7 are still there, just moved around mainly. You can still download and install software the old fashioned way, all the programs I've been using since Win7 I still have. Stuff like Paint are still there, you have to go "Start > All Apps" then scroll all the way down to the W's until you get to the folders Windows Accessories, Windows Administrative Tools, and Windows System. There you'll find all the familiar old windows programs and tools (including the old Control Panel which can also be accessed by right-clicking the Start icon).
Again though, sorry it didn't go well for them. It was jarring for me when I upgraded, but once I figured out where all the useful system tools were rearranged to I was able to get right back to where I left off at Win7. Sometimes you have to endure the change and give it a chance for a few days before giving up. Maybe they can try again one day down the road.