I'm thinking I might fill the hole with black epoxy with the screw in place with plenty of release agent. Any thoughts on this?
Did you strip the threads in the nut? If so, above might work, but I think there are better solutions. Do you own a dial caliper? If not, consider buying one (unless this project is a one-off). Are you familiar with thread standard sizes? Screw head types? Nut shapes? Lowe's et. al. have metric hex nuts, but I would not bet heavily on finding one to fit your screw.
Above said, I'll do ll I can to help you with this.
DDA
