Merlion, I agree with most of what you said. The problem, from my perspective, is when they decided to make Spike a good guy, and they did this through two gimmicks. First, there was the chip in his brain, and second, having him fall in love with Buffy. The problem is, that neither of these two things are really enough to compensate for the lack of a soul. But the writers made Spike a good guy, anyway, when he should have still been evil (he had no soul!!).
The reflection thing as coming from the absence of the soul is interesting. That makes more sense (but it apparently never occurred to the writers, or else they didn't want to confuse people watching Angel, who would all complain if Angel had a reflection). But on the technical side, video cameras and many still cams (I believe, not 100% sure on the still cams) don't use mirrors.
Did Spike want his soul back? That's actually never been clarified, as far as I know. Spike's first words (something about giving Buffy what she really deserves) were meant to mislead the viewers into thinking he wanted to pay Buffy back. But I've always assumed that Spike knew exactly what he was doing, and got what he wanted.