It's been a bit since I did that room. Did that one not open automatically when you have two cats in the room?
You won't get the cat from 10,17 to 10,16, you need to come in from another direction. Take a look at the surrounding rooms and see which ones have two-space-wide exits. (remember to look at the room you will have to come from, since exit and entrance sizes might not match.
On a related question (although how it's related might not be immediately evident) have you learned yet that a dead cat can read signs?