@Reign nailed it @aqua03. It's like when you draw a normal human arm, you don't start straight with the muscles. You have a frame work (stick figure, shapes or whatever else could be used) and then you add the muscle.
All you need to do is layer fur over those initial steps and you should be golden!
On a side note, muscle is hard to show when you are placing fur over it. Have you even seen a naked chimp? Damn those guys are muscular, but their hair covers most of it. Not saying that you shouldn't bother in making muscular characters with fur, but that it can be hard to make them look muscular when their fur is hiding it.
The face looks good in my opinion. It still fits your character while also in that in between space of human and animal. I assume you are trying to go for a Thunder Cats kinda vibe?
Tail wise, I like the cat tail. But the tail seems like more of a creative choice, since it looks really good as it is. If you want a shark tail or a cat one, the choice ultimately falls onto you!