This is the Forms 2.0 library for the Exxact website https://go.exxactcorp.com/js/forms2/js/forms2.js .

I would like to either create or "re-label" the Forms 2.0 library to https://go.sabrepc.com/js/forms2/js/forms2.js .
The image below is the the source code for our SabrePC website

Your terminology is off. We wouldn't say "relabel" here. You're talking about loading the script from an alternate domain or hostname.
Yes, you can load the Marketo form embed from either your Primary LP domain or any valid Domain Alias. And both of those domains are already set up correctly in DNS, so you can use either one.
P.S. Deferring the Forms 2.0 script is dangerous unless you understand how defer works.