About maintaining a digital library loophole found

So this is prompted by me having issues with someone trying to get into my email I have my xbox account on since march. Every time I go under my sign in activity I see at least once a day, sometimes several times a day, someone masking their IP address
has been trying to either sign in or sync my account. I keep thinking someone at Microsoft will see this unusual activity and do something about it on my behalf. Or at least help me contact someone who can help.

Meanwhile tonight, trying to combat this person I noticed I could change my email alias to my Microsoft account. So I go and make a new alias, thinking that if the alias is different then the one they've been trying to sign in through, they'll stop not knowing
what it is now. though haven't removed the old one in case of losing something.

Worried about my Xbox account still being there or not, that's where another problem was found, thus the subject of this forum.

I did some quick looking and found someone on here who acted faster than I, removing their old alias and lost all their digital purchases.

In short:

Anything you buy digitally on the Xbox one is tied to the
email you made the purchase with. Not the Microsoft account

Meaning, even if your using the same Xbox profile, or even
the same Microsoft account, if the email is not the exact same, if you changed your email address cause say, your account was hacked, or you had to change your email alias, or you removed an alias a purchase was made on, those purchases are
unusable
Requiring you to buy them again.

For something you already bought on the exact same account no less.

Shouldn't anything I buy through an account be recorded on said account rather than an email alias I can remove?

If my problem with this mystery person continues and possibly escalates and I need to do something like change my account alias again, this time removing any past ones,
how can I go about keeping my digital game library together for what I already bought?

I've tried looking for something like this under customer support, but as far as xbox goes, everything under help is simple stuff like changing gamer-tags. If anyone can help, that would be super appreciated.

:)