They don't exepereicence many of the emotions we do.
They are not actually vulnerable (that's just a name for the type of narcissism presented). YOU are vulnerable. You are the one dating the abuser. Not them. They're perfectly fine.
They just want you to constantly think of them and their feelings, hence the 'woe is me, my life is so hard, no one understand me' act.
I don't know what feelignd you want them to admit. What you see is generally what you get with them.
I like to explain it as them being the tiger from 'the the life of pie'. You are the boy Pie, swearing blindly to his father that their is compassion in thr tiger, because you have seen it in his eyes. And his father tells him something like, 'no, in his eyes, you only see yourself reflected back at you'.
That's all it is, any goodness is just smoke and mirrors. You are good so you assume there must be good in him. But infact, he only ever reflected your goodness back at you. So he could draw you in and wat you up, like the predator he is.