Why did he put it off? Was it pure laziness, or did he think you might have and adverse reaction to him masturbating?
I ask this because one of previous posts hinted that you may not have been happy about the whole thing.
You feel how you feel and only you can decide if this is really a last straw or self sabotage.
With the best will in the world OP you are not trying your best because you won't consider any help. You can't deal with depression like this it only drags you deeper.
Take a good look at what you've posted. You are going to end your relationship and are waiting till your children are old enough to die( do you mean suicide when you say that?).
Dying won't make it better, that will make it worse. Your children even if adult will break their hearts tying themselves in knots over what ifs. What if they had been better as a child, at school, as a teenager. When someone so close commits suicide the surviving relatives do blame themselves and while they may learn to live with it a lot of joy gets sucked out of their lives.
They deserve a happier childhood than the one you can currently see for them and they deserve a happier mother. You can provide that for them OP but you can't do it alone, no one could. It is not weakness to accept a hand. Many different ways to do it too and lots of people here who have gone through a similar process. You aren't being judged a poor parent, a poor wife, or a bad person. You are being implored to see something deeper in your life is very wrong and to accept help to fix it.