I left my baby standing up in his high chair recently. Cannot believe it. Fortunately both dh and I were there at the time, but we started to get him out of the chair, then I said something about working out what was wrong with the chest of drawers nearby, the drawer wouldn't close. Dh put him down again (seriously, I'm sure it was him!) and we both turned away and started looking at this stupid chest of drawers.
Maybe 30 seconds later we realised ds was standing up, completely unsupported, in his high chair
Cannot believe we did it. Thank god Britney's paparazzis don't follow us too!
Mistakes happen. I hope my fellow Junies won't mention that at least two of them have fallen downstairs whilst holding their precious children, I can imagine the horrific anxiety and fortunately both little pips are right as rain after the experience.
Your dh did not think "hmm, shall I do this properly or shall I not bother, I can always have another baby some other time?" No of course he didn't. He made a genuine mistake and you will make genuine mistakes and there is no way round it but to forgive each other.
I do think, incidentally, that your reaction is partly paranoid new mum (totally sympathise, it comes with the territory) and partly about other issues with your dh, you say you've rowed previously - are you generally having a hard time? This really is completely normal, there have been a couple of threads about it in the last few days.