Klugeryid,
1. Non-Jews can do teshuva just like Jews.
2. Non-Jews being chayiv on pachos m’shava peruta is only if the owner is makpid. Office owners (for most of Romney’s career he was one of the owners) are typically mochel such small takings.
3. I’m not sure what you mean by “saint” (a christian concept) but I have not seen anything about Romney that indicates that he is dishonorable or corrupt in any way.