Sounds like you really have everything under control and know what you are doing. I agree with all your comments.
To be honest, the "proper" way I mentioned to splice is not the way I have done it for 50 years. I just use the same way you do. There are "better" ways like the "western union splice". There are butt splices like the crimp one but you heat melt solder inside them. The crimp with heat shrink over it is just fine for 12V DC lighting. You may get other opinions so you can decide. I should not have mentioned it because I don't do it. Sometimes you can get brainwashed on here. It's important to dress, route and clamp the wires along the way. Also, you can add a ground wire from light housing to frame as redundancy.
You have really made this an enjoyable effort. You followed everyone's suggestions, used your own experience and ability and did the work properly. You found the problem, not us. Good job.
