If as you say you argue rarely then this will feel worse because you rarely argue. Not only because of the kids but because of yourself, iyswim.
A lot of the posters here say that they were scared/hid/wanted their parents to divorce, but those were posters whose parents argued constantly. There is a vast difference between adults who argue all the time and adults who have an occasional but rare heated row.
Adults having arguments is a fact of life and children do need to realise that adults don’t always get on but that they can resolve their differences.
I’m 47 and I can remember my parents rowing precisely because they almost never did. Iyswim. And it certainly hasn’t left scars, I can say “oh, remember when you had that row….” And it’s more of a remembering thing. The children whose parents rowed all the time probably don’t remember the specific one, just that it happened.
You’ve apologised to the kids, now you need to see if you want to resolve things with your Dp.
All relationships have at least one moment where you hate each other/maybe even where divorce is mentioned/you think that you don’t want to continue. It’s life, and actually, in a long relationship it’s normal and it’s human, assuming it’s not regular.
I know my mum threatened my dad with divorce when we were kids. But even she remembers it. When I had some issues with my eXH, before we divorced,my mum said that everyone has wondered at some point whether a marriage is sustainable, the key is whether it’s resolveable or whether things are genuinely at an end.
My parents have been married for 51 years now,and they are genuinely still happy and have been for the majority of their marriage.
But you don’t live with someone for years and years and never reach a point where you wonder whether you really want to keep doing this because they’ve annoyed you so much.
Take a deep breath, if there are issues to be resolved then have a conversation with your DP, but move forward, don’t keep looking back so you can beat yourself up.