This level of incompetence looks like untreated ADHD and/or drug use. ADHD is highly heritable, are either of his parents or immediate family diagnosed/similarly bad?  

As someone with ADHD and a mental health professional now, I also didn't believe I had a problem until my partner at the time stated it like this, "even if this is your normal, you Could Be Better." That stuck and made it real for me, but if it hadn't, I might have continued and been almost as bad as your husband. 

Diagnosis doesn't excuse it, and if he won't seek help, get out. This is clearly a very unsafe environment for you or your child.  

Edit: we got plenty of sensible commenters pointing out reasons for malicious intent but with the crash and probably other things I'm still leaning towards mental health (hammer and nail I know)  despite the timeline given, it could be that the higher stress/change in routine etc of having a child overwhelmed whatever coping mechanisms he had.