That's very thorough! I always wondered how the metal part connects to the flesh part, and I think the idea of synthetic muscles makes sense. I think you're right that his body powering the arm doesn't really make sense, but there's something very amusing to me about the idea of him sitting around charging his arm...

I know his arm being detachable is a popular idea (and I think it's that way in the comics?), but given how his arm is so integrated to his body, I feel like doesn't really make sense for the arm to be detachable without parts of it being dismantled--it doesn't seem like it should pop in and out easily.