Thanks Everett...I enjoyed your post. I only wanted to add two comments.
1. I have only seen bad switch contacts once in my life,
but I have seen it. I never encountered them in my EE career, but before it, while helping my Dad (Electrician) on a job we had it on a brand new light switch. It came straight from the electrical supplier and appeared brand new, so presumably it should have been "good". Installed it and it didn't work. Tested with DMM and got voltage (120V) on both sides, but clearly the switch contacts were high resistance, hence limiting current flow and the light was off as a result. Just wanted to share this anecdote
because it DOES happen, so never assume a switch or relay, etc. is "good" even if it is brand new. Test and verify...
2. I agree on the water heater, but if it can't be easily fixed, I just wanted to give my endorsement for Bradford White water heaters (
https://www.bradfordwhite.com/). I have had several AO Smith water heaters go bad, i.e. crack in water tank and leaked (after 1-2 years of service and they were drained, etc. and maintained). I had much better luck with Bradford White. I believe AO Smith water heaters are imported while Bradford White are made in USA. If you have to replace one, I would recommend considering Bradford White brand water heaters. Just my 2 cents...