My ex who had self-confessed narcissistic traits was like this, he even lied about only having a few years to live, and probably about having been abused as a child and enjoyed it (the details were unlikely-sounding looking back.)
Most people with personality disorders are maybe a mixture of different traits.
Yes, my ex was insecure about some things and he said his boasts etc were an attempt to compensate for those. (Boasts about being a genius to cover up for having a small and impotent penis.)
But remember you can't believe a word they say/do. Even his displays of 'insecurity' could be for something- to keep you feeling he needs you so you have to stick around, or whatever, to make you feel sorry for him or excuse his behaviour.
They wear a mask at all times- different ones for different people.
Mine could even fake having tears in his eyes/being on the verge of tears when he wanted.
Relate counsellors don't tend to be particularly qualified, only basically, and also can have things like a religious bias towards trying to keep marriages together, or whatever.
Towards the end I would somehow see his face as being a mask- there was no way of knowing what truly lay behind it, what he was truly feeling.
He also enjoyed shitstirring and getting a reaction from people, or causing people pain, or at least didn't care about it.
I'm glad you're planning to leave OP and yes, you're right that he's not normal and not nice. xxx