Travis - thanks for sharing your FiL's story. My condolences on your untimely loss. It should make the rest of us that didn't/couldn't serve even more grateful that there were men like him that made it possible for us here and now.
That being said, what several others have said is very true: document, Document, DOCUMENT! Type up a short paper about your FiL, just like you did here. Put a copy with the gun and sword while leaving a copy on your computer (you DO back-up fairly regularly, don't you?). If possible, somebody else suggested contacting a VFW to see if they can put you in touch with a weapons historian. If there is an art or history museum in or near your town, you might try them for references to somebody that could give you more history about the items (including the flag!).
Good luck.