I have a lot of thoughts, and not as much time, so will come back to post more. But if you haven't already, check out smoms.org. I haven't been there in a few years, but was one of the original members in 2000, and stayed till my skiddo became a young adult (he's 23 now). Cathryn, the founder, was a huge inspiration and help for me, esp getting through the teen years. Very supportive forum, and focused on creative problem solving.
You may have to join to post, as I vaguely remember that we were all trying to find a way to make posting more private. Some of us had issues with skids and bio-moms reading our posts. But it's worth the time to join, and a great resource!
More later. Step-parenting is hard!
ETA: I just peeked at the smoms site, and it looks like there's a fee? Hmmmm. I'll be back with thoughts later, not sure when that happened, like I said - it's been a few years since I've been there!