I was surprised by the posts in which people tried to excuse the abuse/redefine it as something loving & normal/victim-blame (you should've said something)/accuse posters of 'looking to be offended'.
Then I remembered how, in talking about my abusive family to people who didn't know them, I would sometimes see people trying to relate what I was saying to their own (non-abusive) background & failing because thankfully they hadn't had to live with people like my family. Sometimes the very word 'father' or 'mother' would set them off defending parents, with no acknowledgement that there are many grades or types of fathers & mothers, some less optimal than others.
I'm not getting at any posters. I just want to point out the dynamics of this.
Those of us from abusive backgrounds often ask, "Is there an 'Abuser's Handbook' somewhere, that they all read?", because their behaviour & words can be eerily similar, even across national boundaries & time. (BTW, yes, I had fat-shaming too, from both parents while I was actually visibly underweight. Helloooo false body image & eating disorder.)
Another thing which occurs to me with all this talk of nicknames is that my malignant narcissist father had derisive nicknames for everybody (child or adult), & wanted everyone except the current victim to join in & find them funny. We didn't. However, one day as an adult I came across a hilarious nickname based on his rank &, thinking it would amuse him too, I used it to him the next time I saw him. Oooh, big mistake! He could dish it out but he couldn't take it. For those new to this, that's a big red flag as to what the power relationship is & whether nicknames are harmless or not.
OP, it sounds like your counselling is going really well. I agree that if you feel it's right, it might be an idea to stop seeing your father. I'd say check out in your own mind who exactly might say you're doing the wrong thing if you do stop (there may be fewer than you assume). Even without your childhood experience of him, his current behaviour would be very upsetting for anybody, & I'm sure most people IRL would understand your not wanting to experience that - I mean, if he'd been a perfect father & then started doing it due solely to the dementia, it would still be appalling. Anyone who tries to guilt you into seeing him is wrong. (Some people might, but this will be due to their own 'stuff'.) Good luck.