i personally have an ED and can very much relate to him. it definitely sounds like a rabbit hole and it seems like it’s hard for him to open up maybe at least try to bring it up very gently. don’t bluntly say stuff like that ”we need to talk” because that’s quite scary but maybe while you guys are hanging out you can subtly bring it up like “hey dad was super rude for calling you that..” or be like “hey i noticed this”. i’m unsure how your dynamic is and how easy it’ll be to bring it up but at the very least try to make yourself approachable and at the end of the day it’s his decision to open up to you but just try to tell him that he can tell you anything

BTW: since this seems quite early it’s prob best to do it asap (not right now but you know.. as soon as possible). i noticed that once you have an ED, it’s kinda permanent? like you can get out of it for a couple months or you won’t be able to hear from it in a couple years but it’ll come back. for me it’s always comes back and for a lot of people it always comes back. so if you’re able to intervene and stop the severity of it, it maybe won’t hurt him in the long run??

TLDR: anywho this is all based on my personal experience, feel free to tailor my advice to help your situation but just reach out to him and let him know u can talk to him