I think that’s an awful way for your “D”P to respond. I think even NT DC will sometimes tell you that they don’t love you.
My youngest has a diagnosis of AuDHD and has said it a few times. We always try and reply with something along the lines of “well I love you every minute of every day”. I might occasionally add “but I don’t like how you’re behaving right now”, depending on how bloody awful they are being…
My DH also found the assessments and diagnosis difficult.
As you probably know, ADHD can be hereditary and for my DH I think he thought that everything going on was just how he was as a child and completely normal. It also doesn’t help that DH and DC2 are very similar on some ways, both exceptionally stubborn, both have ADHD rejection dysmorphia and both, like a lot of people with ADHD they can be a little immature for their years.
If your “D”P thinks that he has ADHD, can he see similarities in how he behaved as a DC? If so, how did his DParents deal with his behaviour?
After my DC2 was diagnosed I’ve sought assessment myself. Is this something your “D”P is willing to do? Maybe going through the process will help him have a deeper understanding of how he reacts to situations involving your DS.
And what tactics is he using to improve his own emotional regulation and how he deals with DS? Things like running, any exercise really, meditation, limiting his own screen time and maybe finding the support of an ADHD Coach?
Ultimately though if he’s not willing to step up an start addressing his own behaviour then ultimately you will probably need to split to protect your DS because yes, right now your “D”P’s behaviour is abusive.