Oh my goodness. I can't express how sorry I am for both you and your sons. My heart flies out to you all. Having been on the receiving end of a very similar circumstance (dad walked out on me at the age of 17 and my younger brother who was 12), I can say that I sympathize deeply.
There is just so much pain involved all around... I'm sorry to see you have to take time away from us, but please, take care of your family first. That should always come as a first priority. I hope for your sake and the kids' that this all gets resolved in the best way possible and quickly.