Never, ever, not even on a blue moon, save anything as normal.dotm except a normal.dotm template created by Word.

I hope that is strong enough! You cannot create a template to replace normal.dotm and have a fully-functioning Word system. I know some people who might be able to do that, but I am not one of them. I do not know any of them who would try to do this.

That said, you could Open your normal.dotm template and make the changes to it directly. How to Open the Normal Template in Any Desktop Version of Word (except Mac 2008)

If you have already saved something else as normal.dotm, rename that. Let Word create a new normal.dotm for you, then open and modify that.

That said, you should not be putting any text into a normal template.

Here is a way to have a different template used as the default for new documents without making changes to the normal template:
Easy New Document Template Package