If they have his real full name, it wouldn't be that hard to verify his military service even as far back as the Revolutionary War. The National Archives holds records relating to military service during the Revolutionary War, including both Continental troops and state troops that served as Continental troops.
When RIP realizes that he's in 2022, he faints. After waking up says that he just had a nightmare. The whole scene is very similar to the ones in Back to the Future (1985) and its two sequels when Marty McFly wakes up after hitting his head and says that he has a horrible nightmare. Both movies shared also the travel into time theme.