Thanks for your input all.
Here is where I stand, and some answers to some of the questions that have been asked.
Yes I knew he had a disability before I entered the relationship, and yes I was ok with it. The unfortunate part is that one cannot really know to what extent the disability is until one lives with it on a daily basis. Over the course of a couple of hours it does not seem like such a big deal, but when one is faced with it 24/7 the little things compound. Anyone who says differently doesn't know shit about the situation. Yes the boy is both on drugs and in therapy, to the extent that we are able to pay. Much of this does not come cheaply, and we are not 'wealthy' to the extent that this does not hurt the bottom line, but we do what we are able to. As for the father, he passed away when the lad was a toddler, I am dating a widow, so of course no help from that angle.
I understand (probably better than most people), what it means to date a woman with children and to take on a new family. That is one of the things I thought long and hard about before entering the relationship. I have kids myself. Would a single woman be able to get into a relationship where the man had kids and have to take on a family? Would she understand that the kids ALWAYS come first? Would she want kids of her own some day? Does she understand what having kids entails, and that you can't just send them home at the end of the day? These are all things I thought carefully about before dating a woman with children. There are those that think a woman with children is 'damaged goods'. Could the same be said for a man with children? I believe no.
To anyone that thinks I don't love these kids, you have no idea. The decision that I have to make not only affects myself, but my SO, her kids, my kids, and to an extent my ex-wife as well. Though I do love these kids to death, is it fair to my own children that their life has changed so drastically? There are times I do not see my own kids as I am at doctors appointments, school functions, or babysitting (parenting) my new family. No, I do not have animosity for these two kids, that is not like me. They are both very loving children that deserve nothing but the best. The issue is with me. Am I capable of providing (long term) the love guidance and affection that these children require without sacrificing either myself, or any of the other people involved. That is the big question.
No I have not made up my mind, no I am not just looking for justification, no I have not started seeing escorts again as an escape.
Again, I have to think this well out, as the consequences of my actions (either decision I make), will drastically affect the lives of many of the people I love. I did not jump into this relationship both feet first, I thought long and hard about every aspect of it. Unfortunately, one can not predict the future and be able to see how things will 'really' unfold. Again, I do love these children, but the decision that I make must be in the best interest of EVERYONE involved, not just myself.
ps. Thanks for all the input folks, and for keeping the discussion civil and sane. You have all given me some very good points to consider.