Re: How do I stop the video app from keep asking for my xbox sign in.
It's not an "MS email account" anymore (like a live or hotmail email account). Now, it's a "Microsoft account", which covers the whole ecosystem and makes everything work and sync together... On your phone, you'll need to add this Microsoft account under settings/ email and accounts. Then, once you have that set up, all the apps you get on your phone will be tied to that account. Also on Windows 8/8.1/10 PCs, you'll want to sign in with that same account so everything you do on your phone (apps, OneNote entries, OneDrive, etc) will be available on your PC as well. Same goes for Xbox.. Same Microsoft account (if you have one... if not, don't worry, i don't either! But I still have Xbox games on my Windows phone where I earn achievements etc)
Then, if you ever need to reset your phone, it'll ask you the first time it starts up for your Microsoft account, and you'll be able to restore all the apps, settings and contacts associated with that account. Get it now?