I am sorry you are feeling down, Clod. I don't truly know what it is to cope with this kind of situation, but I can imagine it would be something I would not easily cope with. You are doing magnificent, however. Your dedication and strength in this difficult time are showing through even just in your text. Don't give up. Your little boy is a lucky, lucky kid, you know. And you will get through this. Maybe it feels like your patience is beyond repair or that you just can't take another day. If so, remember that every day...every moment is fresh. Take a few minutes every day to just breathe. Take some time for you...do something special for yourself, if you can.
Feel free to use PM if you need someone to talk to.
I can relate to the step kids coming for the summer. We also have my husband's children in the summers and it can be taxing for everyone involved, trying to adjust to the differences in households, trying to recalibrate everyone's understanding of how we do things in our house, etc. And I am available to watch the kids, yet, it is usually a stressful ordeal. Last year I put together a weekly schedule which included themes and activities. I posted these schedules on the wall, so the kids knew what we were going to be doing on any given day. It seemed to help diffuse some of the chaos.