I personally downloaded Grim from the exchange and haven't had any problems, although he does like to pop up in CAS and give me a fright
. As for what Reaper babies would look like, I used the skin to make a Sim and put her in the game.
This is Tinsel. She's got a few issues with the shading at her shoulders and other joints, but otherwise I think she's very pretty.
Another note: You mentioned that when you tried to change the Sim's skin colour, they still looked a little glossy. You can fix that be using the CAS tools to Create a Twin. As long as the skin colour isn't black anymore, the Twin shouldn't have the glossy effect. I think it just exists so we don't have to look at a totally dark, featureless Sim if we do happen to get the skin.