Hi Robin and

Validation is a skill that takes some practice and time to develop. I wouldn't say I am good at it. I am at least not horrible.

Reading the books, and using the examples I found in the books didn't get me too far because the examples in the books weren't in my own words, and probably sounded stilted or odd.
SO is so terrified that he will be alone, without DBT or other skills and that he will be homeless and have no one to help him. He says over and over again, what am I going to do when you're dead (you aren't going to live forever). I say I'm right here and he gets mad and says I'm not listening. He is so fearful he won't move forward.
For me what I found to be helpful is to acknowledge what ever the feeling that is being expressed first. If my partner is expressing fear about left alone and vulnerable, my first job is to recognize that feeling. Something simple 'yes that can be a scary thought'. Before I can explain anything I have to acknowledge the overwhelming emotion.
You're not alone Robin, this is not easy stuff, it sounds simple but it's definitely not easy.
How long have you and your SO been together?
'ducks