I'm happy to say I've found my rhythm. Both stories seem to have a good pull and voice at different times of the day, which works great.
Are my fears of similarity gone? No, not completely. But, I'm dealing a bit. I think at some point, that little voice that questions my every word, sentence, paragraph, page, etc. will go away. I just have to push on, right? I just have to breathe through and know that its going to work.
My novel-in-progress has also not lost steam, for which I'm grateful. I don't know about anyone else, but writing two things at once can be daunting. Its not impossible, though. It also helps that the two stories are very different. Sometimes, I'm on autopilot, which is wonderful. When the words flow....its a good day. 8)