Two things about Bennings assimilation that confused me.
1. It's hard for me to believe the slow moving thing was able to get Bennings. I'm guessing the split face thing slowly starts reassembling itself, very slowly crawls on the floor, and then grabs a hold of Bennings' foot and drags him over to assimilate him according to the [bright red] blood trail. It was hard for me to fill in the blank and picture how Bennings was assimilated. It's like picturing a sloth sneaking up on me and putting me in a choke hold.
If it grabbed his foot, he could possibly get away or scream for help or chop it off. But the most logical way I could guess was the split face thing made a lasso tentacle (like Palmer thing) and grabbed his face and then dragged him over and assimilated him.
2. Casually taking the split face corpse outside to burn it well done. I'd be afraid to get anywhere close to it seeing that it was clearly still alive. There's probably some pieces of the thing still waiting inside. Just picking up the split face corpse, it could probably do the same thing to them as it did to Bennings.