Not really happy with this photo (not much distinction between cat and background), but my other choise was a not so tasty fish I found in my grass this morning. This is Neo, one of our cats. Don't know if she catched the fish. When I came home this evening the fish was gone!
You know what might really help this??? Choose the levels layer and make it dark until the background is the darkness you want, Completely forget about the cat and work on the background. Once you have everything where you need it choose the paint brush and the color black and paint the cat. It will remove the mask there and should lighten up the cat. Hope it helps.
OK, can't say anything more than what you've already said about your picture (you know where the weaknesses are). It seems to me that we take better picture when we're happy with the subject. Any time I've taken a picture "'cause I had to", I was disappointed by the result. You'll do better tomorrow. Yesterday's shot was really nice, especially the sky.
PS: I saw the fish in your portfolio - you are better off with the cat!