That's very interesting indeed. I did smoke in the past before as well and I also had a lot of mood swings, but when I quit I didn't think that smoking was the cause of it, because when I was quitting, I also started meditating at the same time and I thought that meditation was the main reason my mood swings disappeared. But I guess smoking was affecting me emotionally as well!
It's crazy how much damage smoking does to our bodies and mind, but a lot of us still do it...
I can relate to the energy part as well. When I quit, I felt like on top of the world and I started needing much less sleep to feel fully refreshed. Glad you're quitting this horrible habit :)