Microsoft Account Hacked

ShootingStar_171820

Hi, a couple of months ago my partners Microsoft account was hacked, the first few times he managed to change the password, but then the last time he was hacked, the email addresses that were added to the account were Russian, his emails were removed as was his security information etc. Fast forward through two months of phoning Microsoft and getting absolutely nowhere just more frustrated and a higher phone bill. My partners ex's son's Xbox account is attached to this Microsoft account and he's been locked out of that, again no help anywhere. Microsoft have basically said that because his security information was removed and his two-factor authentication and because the hacker changed this to their details, Microsoft has said there's nothing that they can do about it and case closed. 

My partner is still getting emails from sites like Facebook (though Facebook is sorted now) EA and Twitter have all been messaging him about the fact his passwords have been reset etc. So if someone hacks your Microsoft account can they gain access to all his emails as well etc. 
He doesn't know how they hacked him initially, he's careful online, we don't share xbox details, and his passwords aren't easy to guess. But there seems to be something new all the time getting hacked into even though Microsoft state that they have suspended his account but obviously they haven't and they don't care about him getting his account back either.