I believe those texts are real; however, given that he's already been proven to be a scam artist (look at the unemployment scam he tried) I wouldn't be surprised to find out that he isn't telling the whole story or taking individual messages out of context. I also would not be surprised to find out that his whole family is made up of hot headed lunatics that need some serious therapy.
I wanted to add this: I don't believe for a second that I'm talking to his real "sister" - the Facebook photo of her is way too hot and feels like it was designed to get a loser like me interested. Also they linked me to this thread. I believe I'm talking to another sped like him. I'm aware that it might be someone he owes money to, possibly even his drug dealer. Or possibly some Fortnite player that got too mad at him.
However, a lot adds up. His speech patterns match that of someone with mild to severe brain damage, and the video where he shows off his cut arm matches that of an emo teen that cuts themselves with a straight razor (nevermind that a nearly 70 year old man isn't going to simultaneously push you down the stairs and cut your arm in multiple places with a fucking butter knife).
Also nearly 100% of Greg's argument was that his dad was mad about a cut up rug, but in the text you can clearly see that someone is mad that Greg didn't clean his room like a good autist
TL;DR: Greg is a giant liar that thinks you can buff cuts out of your arm and that mice lay eggs. I'd feel bad for him if he wasn't a 43 year old drug addict that got kicked out of his dad's basement for not cleaning up his cesspit.