I know its possible but not 100% on it. Can you have alfresco web running on one server and alfresco share working on another? This is part of the solution i have planned for external access within my organisation. If so is this mentioned anywhere in the setup / wiki files? Can't see any mention of it.
Do you mean have the alfresco WAR (ie, the repository) running on one server and the Share WAR running on a separate server? Yes, definitely you can do that. It's just a matter of config. There are multiple places where "localhost" is specified in the out-of-the-box config files that would need to be changed to reflect your actual host names.
If you can't find them let me know. I might have an example somewhere but it will take some digging to get to it.