Normal is relative. What's normal to 你 may not be normal to everyone else. People can be sadistic without being sent to an asylum. I have sadistic tendencies but I won't go out and murder a town 或者 anything like that. As far as I am concerned as long as 你 don't try to kill people 或者 mutilate them 或者 anything like that. I think you're fine.
I mean everyone to a degree has the possibility to be sadistic. 你 might need to try and practice empathy towards people 更多 often but I don't think you're that bad for being happy when someone cries.
I guess I'd need some 更多 details on your mindset, like: are 你 the one making others cry? Is that the only thing that brings 你 a sense of happiness? If so, then you'd probably want to be concerned.
As far as feeling sadistic, I think we all feel a range of emotions. If this is the only way that 你 feel, again, 你 should be a bit concerned.
I entertain dark thoughts as much as the 下一个 person, I suppose, but they don't occupy my mind constantly. I also laugh at inappropriate things, but I think that's 更多 a nervous reaction. Well, that's MY story anyway.