I know your pain, and I am sorry you are dealing with this also. This was a big part of Wiz for a long time. One of the things that helped was when he started the "you don't love me" and the "you never do anything nice/fun/whatever with me" was when I pointed out what I did do.
I would say things like, "Of course you don't have a brand new book in your hands, bought today, the day it was first sold anywhere ever, because I don't love you. I have NEVER taken you to a soccer game and cheered for you. In fact, you are walking around naked because I don't care enough to make sure you have warm clothes when it is cold out." I often reeled out four or five things that we had just done, eaten, purchased, cheered or otherwise engaged in just for him. It had a habit of opening his eyes, and if nothing else, it stymied him enough that he stopped talking. Some days that alone was more than enough to make me happy.
I don't know if it would helpw ith your son or not. I did it out of sheer frustration and was rather surprised when the therapist and psychiatrist said it was an excellent thing to do. A few years later he went back to that koi, and I went into his room and boxed up everything that I had given him or bought for him or created for him. I told him that this is what his room would look like (almost completely empty) if I didn't love him, and if he EVER pulled that koi on me again, I would allow him to live that reality for a few weeks or months before I let him have the stuff that I gave to the child I love more than my own life. He could then make an informed decision on whether he wanted to live as though I didn't love him or if he wanted to stop the BS and admit that he knew dang well he was loved.
It was a TOTAL shock to him, though I had been planning it for a couple of weeks.
I can tolerate a lot. I don't give a hoot if they hate me because I made them do chores or homework or didn't buy every little thing their hearts desire. But not acknowledging that they are loved? Not okay with me, and sure as sugar not okay in my home.