If you forget your username several things you can do.
1. in apps and accounts your username should appear.
2. if you have emails from microsoft about your account your username will appear.
If you sign into office and open the app of your choice your username will appear.
If you can create a local account you can get back into your computer.
If you have another system with skype on it chances are that you can get your username from there.
If you have friends on skype ask them what your skypename and or email for your microsoft account is, chances are they will have it.
However to avoid this stupid situation.
1. if you have a backup of your data and you really should the easiest way is to reformat and reinstall windows that will get you back in.
2. make a local account you can use a password or not up to you.
Next add your ms account in apps and accounts.
This is how I do it, its less dangerous without not logging in.
I had this happen to a friend's system, a good reformat and restore of all the data and setup as I said and we don't have a problem.
At any rate I have given you at least 5-6 ways to find your password.
Sadly ms website is not helpfull, I guess you could ring microsoft for it, you are using an alternit email address, ask microsfot support and tell them you forgot your username, if you can remember your password they can probably email your userid at you.