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As you're experiencing - without respect, there is no relationship. So if you can support youself and your childeren - I would suggest leaving, and doing so because it sounds like you'd be happie without him in your life.
But, if you decide to stay - start living your own life... cut him out, stop expecting anything from him - you say he's never on time - don't ask him to do anything - do it on your own - that way, he can't disappoint you by being late.
If he's not wise - don't ask for his opinion on anything
If he's not reliable - don't rely on him for anything - become self-sufficient
If he's a liar - don't give him the chance to lie to you
If he insults the kids - don't let them be around who would do do
If he's lazy - get busy and be gone a lot
And so on.... cut him out of your life - son't have any expectations - that way - he can't disppoint you.