I want to know: How do you need to be validated? Or what makes you feel that your feelings are being validated by the person you love?

I fully, fully admit, I have a really hard time listening and validating when my pwBDP is having an episode that includes paranoid ideas and dissociative thoughts. Especially if they involve me. He often says he just wants to talk about how he is feeling, but him "talking" is really just interrogations, unreasonable requests, hypothetical questions, circular conversations to trip me up...etc. I have a hard time not becoming defensive, especially when it involves irrational jealousies and things that I know I would never do. My mind automatically goes to "well if he really cared about me at all, he would know that I'm not the kind of person that would cheat on him," or "why doesn't he look at all the other things that take place in our relationship that prove the love I have for him when he feels this way?" 

As someone who previously came from an abusive upbringing and was made to constantly feel less than worthy and never good enough, (me - the caretaker, looking for a healthy way to balance this all,) his feelings and accusations trigger me in a way that I feel like I am being put on trial again to prove my self-worth. This then internally triggers the fear that he doesn't think I'm worthy, so why am I wasting my time? Which THEN in turn makes me feel resentful for everything that I do for him to take care of him and make him feel loved, because I don't feel like it is acknowledged or appreciated. :/ You get the drift. NOT helpful. 

Is there a good way to ask him to express feelings without accusations? And even if something he feels and believes is REALLY out there and far-fetched, is it okay to validate? I guess one of my big fears, is that by validating his feelings, when I believe that they are irrational, he will start to look at them as "facts."

So I guess the big, all-encompassing question would be, how do I validate feelings that he wants to share with me, that I find irrational, (but obviously he doesn't because they are causing him very real pain,) and make him feel supported, without agreeing in a way that might, (I fear,) cause more problems? (I guess the reactivity would be something I would need to address personally.)