I'm just going to be blunt because I don't like hearing you struggle. It's your time to be selfish. You and the Mrs. This project is yours to enjoy a cool road trip that most of us nutjobs would give anything to go do ourselves. Shut it down and take the time to do your project at your new, slower pace. You have earned your 2nd or 3rd retirement to slow down and enjoy just tinkering away at your own stuff vs breaking your back on others' projects.
I know it's not your nature to turn away from helping anybody, a friend or paying customer, but something has got to give. Right now that something is you. Your mental capacity for problem-solving, and physical strength are all getting used up doing stuff for others. This leaves you frustrated and befuddled looking for a damn stud and nut you had in your hand five minutes earlier.
I don't think I'm alone in my thoughts on this. You need to take care of numero uno. I hope you do.