If people could see in the dark, would crime be higher, or lower? (At night. )

According to this, the only types of crimes being significantly more prevalent during the night are rape, sexual assault, and car theft.
Though I think that is due to less people being around at night to see you do it/ stop you, and not due to reduced visibility.
So, no, I do not think that crime rates would be affected to any statistically significant degree.

It really depends on the person, but in both cases, it could go either way. For example, the black market rate could go up, but at the same time, they could be catching more black market sellers. It really depends on the place and the people there, but I do like the creativity in the question.

Haha, funny question!
Yes, as @lavaLava4lamp said, it would depend on the people and area. It would make it easier to catch mice and rats like a cat though.You could crouch in your kitchen and pounce on mice in the dark. lol