Perhaps a new tack is needed. There is also corporate philanthropy, companies that give funds for purposes, one or more of which might be interested in your project.
You must continue to create the project, the film, with or without help, continually amassing material, identifying where it can be found when you're ready for it, creating actual footage, writing the script for narration, still photos, documents, etc. The more complete the project is, the more likely others are to buy in and want to help you complete it and go to market.
As for the museum, someone in government at some level would love to have another tourism draw to add to the tourism and cultural mix in their locale. You need to find out who and where they are, and maybe interest more than one, to get them competing for it, supporting the whole project. Good luck. Such diligence will be rewarded in the end, and all the sweeter for the struggle.

There will always be another song to be written. Someone will write it. Why not you? www.garyeandrews.com