It looks like a second gamer tag has been associated with my account

No, this did not help me. The gamer tag is still active as I can look it up from another account and even send it a friend request. When I look it up it is definitely my profile and it say original Xbox user. So, the account is still active and my problem
is not the gamer tag, its logging in with the e-mail address associated with the gamer tag.

Hi KC,

Thanks for coming to the forums. Unfortunately, there is no way of removing the suffix. They added the suffix so many people could have same gamer tag. Example if multiple people wanted John smith then the suffix gets added to tell people apart. When making
a gamer tag, it will show you what the gamer tag will look like. If it is a unique one that no one has it will not show the suffix. Please make sure you check these when going to change gamer tag. There are a few gamer tag checkers out there that are not correct.
Here is
the FAQ for the gamer tag update.

Thanks,

Brad

Hi Brad, the gamertag I changed to and using now was unique. I did previously have it linked to my second microsoft account before I closed the account. I changed my gamertag on my main microsoft account to the gamertag I had on my second microsoft account
once that account was fully closed.

As my other microsoft account was closed, surely there wouldn't be a suffix generated next to the gamertag because that account no longer has the gamertag tied to it?

Hi.

So the gamer tag associated with my email (the adult) is there to stay or can I delete that gamer tag and create my own? Then I could create a new profile for son #1 and a new gamer tag.

I have figured out/created a new profile and gamer tag for son #2.

So I would like to:

change the gamer tag that is connected to my email account (the adult).

If possible I would like to keep my son's gamer tag and just move it to the email account/profile I created for him... (I'm pretty sure you said I couldn't do this but just checking?

I logged on to my live account and it's does not have my gamer tag RAPIDxxKAOStagxx27 instead there's some gamer that's not associated with mtg account. Why is this?

You can contact xbox support by going
Here and they can look the account up with your gamer tag and if they can verify ownership of the account then they can give you the email address associated with the gamer tag.