My stbx used to tell me I was the craziest person he knew and all kinds of other terrible things. He used to mock me for everything. He was just projecting. Would you get mad if your 4 year old got mad at you and called you a poopie head? Well you have to apply the same set a principles here. Your ex is extremely immature. If he can't even support himself without his parents help he most likely has some serious self esteem issues. The next times you have to deal with him and he starts abusing you either abruptly end the conversation or don't even try to defend yourself, just say sometime like "I see, sorry you feel that way" and turn the conversation back to your daughter or whatever the reason you are speaking to him in the first place. believe me this works I've been living with an abusive man for years and if you don't respond (falls on deaf ears) they do start to see that it's pointless to even start, they are looking for a reaction.

If I were you I wouldn't delete the emails. Just create a fold and store them in there in case you need it at some point. Sounds like he's the unstable one so you might want to keep some documentation of that. Also let him file away with the court. The most custody he's going to get is 50-50.