Boyfriend hurts me physically for fun, likes to watch gore: Should I be worried?

I have recently entered a relationship with a guy who is smart, good-looking and has a great personality. We are both in our 20's. He gets along with people great and everyone who meets him loves him. I sometimes wonder about the things he says or does though. I'll just dive into it:

He has mentioned a couple of times that he was cruel to animals when he was a child. It is of course in the past, but I have heard that this is not necessarily a good sign when it comes to future behavior.

He has shown me a website where he likes to watch gore. That is, disturbing and real images and videos of people's heads blown off, serious injury, bloody and messy executions etc. He says he watches it because it is fascinating to him to see how to body works, but I think it's a little scary that he doesn't seem to care that he is watching real people suffer like that. He either shows no reaction to it or comments on how many hits of the axe it took before the foot came off or similar. He seems rather disattached to other people's feelings in other parts of his life too, but luckily he seems to care about mine.

What complicates things a little is that I am a masochist sexually, so I enjoy some pain in bed. He says he does not get turned on by hurting me and that he's not a sadist sexually. Still, he does do sadistic things to me in bed, which I have interpreted as an attempt to please me. He sometimes slaps me across the face hard "just for fun" outside of bed, which I thought was him just blurring out the lines between sex and our normal mode. It has bruised my face before (not that it matters, but it speaks of how hard he slaps).

Today he got out a scissor and cut me with it (using it like a knife) with no relation to sex. He was unsatisfied with the scissor because it was not that sharp, so he had to go over the same area of my skin with it again and was disappointed it did not draw more blood than it did. It hurt quite a lot and I told him that. I found this act rather surprising as it was so separate from sex and as I have been very open about what I like and dislike, he knew from before that it was something I would not enjoy. I get the feeling that he enjoys hurting me, but in a non-sexual way.

I guess I just wish to understand why he is like this. I assume I have nothing to worry about in regards to abuse as he has not acted aggressively in anger before, nor have I ever even seen him angry. Do any of you know what might make him interested in these kinds of things? Please help me understand him