I wouldn't describe the actions as psychotic at all. There's no indications that she has hallucinations or delusions. Just anger at being told to F-off, which at worst I would say is a sign of young age.
While blowing up and throwing and breaking things does seem a bit extreme to someone of my age, I'm also aware that age has brought me wisdom and patience that I didn't have when I was much younger. If I were in my late teens to early 20s and someone told me to F-off when I was asking them for help, throwing a
tank into the wall wouldn't have been out of the possible responses I would have had either. Especially if I was asking for help with my baby. When my daughter was a baby I was the primary caregiver. I not only changed and fed her on a regular basis, I was the one making trips to the pediatrician, getting up in the middle of the night to take care of her while my wife slept, missing work when my daughter was sick (And she had a REALLY rough stomach virus once where she was vomiting for 10 days straight, and couldn't even hold down a single teaspoon of liquid), etc... My wife was at a new job that required a lot of overtime and I took over the primary responsibility for caring for our daughter. My wife and I had been together for 7 years at that point, but I would have blown up at her if she had ever told me to F-off when I asked for help, no matter how trivial the help I needed was.
In many ways I can relate to the mother's side of the issue more than the fathers, despite being a male myself. Does it require two people to bathe a baby? No, it really doesn't. BUT... if she's already put in a full day of caring for the kid, plus possibly having her own job to deal with, plus the normal domestic issues that we all have, she should certainly be able to ask for a bit of help and have every expectation that he give it without complaint. It's just as much his baby as it is hers, and she's already doing most of the work. He can certainly give any care for that child that is asked of him, and he should without question or complaint.
And he needs to keep in mind that this is just the beginning and it gets harder as his child gets older. My daughter is coming up on her 14th birthday and it's not at all unusual for me to come home from work and only get 15-20 minutes to sit and rest before I spend the next 2-3 hours helping my daughter with her homework. I rarely get to do what I want until well after 8PM. But that's the responsibility I signed up for when I got married and had a child. She comes first, ALWAYS.
And I wouldn't have it any other way.
My advice to the OP would be to remember, there are no do-overs when it comes to parenting. Get it right the first time and the results will last a lifetime. Get it wrong and that too will last a lifetime.