how do I keep my xbox live account.

Keep auto-renewal turned on.

yes the game tag/account can be used on both the 360 and the One.

Here is a suggestion If you have your Xbox live account under My home Xbox you can basically game share with yourself and can use the Xbox live on both accounts and do not have to pay an extra $60 on another account, but keep in mind you will on be able
to you Xbox live on both accounts only on the console your do it on because you are basically save the receipt of the Xbox live account to your console. Keep in mind you can only do this 5 time yearly.

Here is how to do this. go to setting > General > Personalization > My home Xbox> Select make this my home Xbox.

Your Xbox account is same as a Microsoft account. You can delete your account in Xbox, but no more.

Hey Glenn, I understand your frustration with this issue. Unfortunately, it's par for the course with all the major tech companies. Google and Apple also tie all of their services into one account. E.g. When you sign up for a gmail or google drive account,
your account info is shared among all their services; photos, youtube, play, etc.

For a majority of users, they don't mind this all-in-one approach, some actually prefer it because it makes things simple. But of course, there's a group, like yourself, who don't appreciate this feature. They should have an opt-in feature for those who'll
never use certain services like xbox.

Not saying it's right, but personally, I haven't found greener grass with any other tech company. Microsoft's security is up there with the best of them.