waltermittymissus is spot on. He IS gaslighting you.
Youre not being insecure at all.
& yes..narcissists, manipulators, abusers & mindfuckers have very good form in attending counselling sessions and twisting the advice given into another stick to beat you with, metaphorically speaking.
He wants either the mother or the daughter (she is now a grown woman, is not his biological daughter and I dont buy that, it would be entirely impossible for him to have developed feelings for her) but, I think its most likely the mother he is after. Probably gaslighting her too, parading her and there with her daughter. Do you 2 have DCs?
OP, dont be fooled by anyone who tries to tell you, you are jealous or insecure for daring to question his activities and motives instead of playing the oh so cool lady who is implicitly trusting of every single female friend..and if she isnt, she has ishoooooos. Then again, I know you arent fooled, really. Your intuition and gut instinct are rightly telling you that this situation is not on.
Re. your row..you hadnt any ideas about where to go. Rather than come up with something or at least suggest you have a think together, or just be lighthearted about it, he pounces and turns it into a row. Wasting words and time..when it would have been quicker to come up with a suggestion!
Im sorry to hear of your situation. Being manipulated like this is horrible. Think things through, and make sure to take care of yourself. Put yourself 1st..thats what your partner is doing, after all. The row situation would have got on my last nerve. He needs to piss off you sound way too good for him. A man who doesnt know what he wants, or wants a foot in 2 camps, can do sweet f.a. for you. An emotional vampire in your life you do not need. Its hard, when you love the person who is treating you this way. But in years to come you dont want to look back to find, he's flattened your self-esteem. Make a stand. He will either come to his senses, or ship out. Either way, you'll know whats what. Good luck.