Moving a gamertag to a different microsoft acount

Hi JonCook2, sorry but 2 different Microsoft account are 2 Xbox Live (and Gamertag) account different. You can't linked stuff from one to another.
The only solution you have eventually is contact the support, ask for a refund while explain your case, hope refund works and re-buy the DLC with the correct account.

Unfortunately it says I cant add an email linked to another Microsoft account

You could try to add it under account alias's

I'm afraid this is not possible. An account is linked to an individual and moving things related to that individual to another account (i.e. most probably another individual) is not standard procedure.

However, perhaps this could be achieved if the case at hand is well explained to the official support team.

Alternatively you might want to consider two other options:

1. Rename/add another e-mail address to the existing account so you can keep using it, and your father can move to another (new) account, setting up what he needs there.
2. Register multiple accounts on you guest console.

I highly recommend taking ik up with the official, friendly support xbox support staff. Do know however, that they've been swarmed with questions the past few months, so it may take a while before your question gets answered by them.

I suggest you use
the green "contact us" button on the right side of this page.

it is still possible to do, but would be a pain.

you would have to sign into the account with the email that you "want" to use for your account at
https://login.live.com and then close it out, by clicking on security and password (you might get prompted to verify and email or phone number) then scrolling to the bottome and clicking close account, follow
those prompts. due to the email that you want to use is an outlook, which is Microsoft controlled, you will then need to close all that out and sign into your email. it takes 60 days to completely close the Microsoft account attached to that email. once it
has closed, you can then try to use it to do the swap.

NOTE: If you have purchased anything under the gamertag that is associated with the outlook Microsoft account, you will loose it. there is no way to merge accounts to keep that stuff.