Why not sell it on APUG? That way you know it will go to somebody who will use it. Maybe you can contact a high school or college photography program near you to find a student who has discovered film. The school itself won't want it, but young people do show up here now and then, rebels from art schools who want to go their own non-digital route.
I can't help you about downsizing, as I have been upsizing from 35mm to 6x6. We are only a few years younger than you and we tried to downsize in our last move, but ended up with the same size house. Our downsizing project now is to get rid of the 30 years of accumulated junk while adding a darkroom! Good luck with yours.