Wow! You've got quite a lot in your post. However, I picked these gems of wisdom
The first thing that comes to mind, is that I must not stick my nose in other people’s relationships
Don’t interpret other people’s feelings. Don’t say how someone is feeling if they haven’t told you they feel that way.
Don’t say what someone wants if they haven’t told you that’s what they want. Just don’t put words in other people’s mouths.