Can I delete an Xbox account thats attached to my main microsoft account, then switch the...

no, the xbox account IS the microsoft account. delete one and they both go.

I never signed back into my Microsoft account during those 65 days and attempting to do so yields a "this email is not recognised" message.

I either "deleted" or "closed" it, I can't remember the exact wording of it. Main point is I had a Microsoft account with an Xbox account attached to it and closed the Microsoft account in an attempt to delete the Xbox account. I also wasn't using either
account, so I intended getting rid of them both by deleting the Microsoft one.

Translation: I'm Poland! You can delete an xbox 360 microsoft from my account so I can create a new account?

Hi there,

a xbox live account can not be deleted from your Microsoft Account, you can only move it to another Microsoft Account (and if needed Close that Microsoft Account).

See this link for the steps and limitations:
support.xbox.com/.../switch-gamertag-to-different-microsoft-account

Hi and thanks for reaching Microsoft Xbox gamer's community. My name is Josef.
I'm an Independent Advisor and a Microsoft Xbox user like you.

Hope you're doing great today Liam

It's not possible, actually there is no way to transfer Xbox profile to another microsoft account
Even if you delete the main alias attached to it

All content, including Xbox purchases and in-game progress and everything are attached to the Microsoft account

Sorry

The only way to delete an Xbox account is by deleting the Microsoft account attached to it.