Hi @3dmodelfree,
What you are asking is almost impossible to do. Please note that your fallback cache is not a HTTP request that you will do 301 redirect to another URL.
The way fallback cache works is that when a request comes for a page the Cloudflare checks if that page is in their cache and if it is then provide it from their CDN. If not the request comes to the origin server and the plugin grabs the request to check if there is a fallback cache already generated for that page, if there is then the plugin provides that already generated fallback cache HTML version of the page to the request and the user sees it. In this way the origin server didn’t had to do much work to regenerate and recreate the whole HTML by running the PHP.
If fallback cache is not present for that page, the request is passed to the server to generate the HTML and send to the user which ofcourse takes more time.
There is no way to save the fallback cache on a different server and then to check if cache exists open a new connection to that new server and make CRUD operations there. Sorry man!