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It would help me formulate a more complete answer if you could elaborate a bit on why the two of you have split up so many times. Also it would help to know what changes you want him to make.
I look forward to hearing from you and working on this with you,
With him not wanting to get any help and placing all the blame on you, the outlook is not too hopeful.
It is hard enough for a child to lose a parent through divorce or accident, but suicide adds a level of guilt to the equation....did I do something to cause it, did I not show him I loved him enough, could I have prevented him from killing himself,? etc. --mixed up with anger at his father for choosing to leave him. This almost certainly had to have been a traumatic experience, and would quite naturally affect his ability to bond with and trust others. His narcissistic behavior is most likely a defense against the hurt of having his father make the choice to leave him forever.
If you want to try to work on the marriage to keep the family together, I would strongly suggest that you work with a supportive therapist to help you set boundaries on his behavior and his blame. Here's a link to help you find someone local. Another way to get that kind of support, if you can't afford a therapist, is to try one of the twelve step programs such as Al-anon or CODA. These are groups for people who have been affected negatively by other's behavior. Both these groups main focus is the setting of boundaries so that your own emotional peace isn't upset by someone else's behavior.
You have a hard road ahead, whether you decide to take him back or to try to raise the children on your own. I wish you all the best,