What are signs that a "player" has really changed and really fallen for a girl?

When he doesn't seem like he's trying to get in your pant. It's that simple.

I know a co-worker who used to be a playa in his early days, but now he's settled down with this wonderful woman and has two kids. So it is possible that a playa can be matured and retired from their game.

From what you said, I believe he changed. Because a playa won't waste that much time talking about emotion and love crap other than to try to get in your pant with his charm and game.

I think he wants to change, and really likes you.

I don't know about signs, but your description reminds me of a young man my daughter knew as a teen. He was a player, following in his older brother's footsteps. When the brother got a girl pregnant, something about that must have scared him or got him thinking. He realised girls didn't respect him or his brother, and that motivated him to change. And he did. He started pursuing a different sort of girl. Then after getting dumped a couple of times, he got better at learning how to treat them. He went to college, struggled at first, but kept trying. He got a job and kept going to school. He got an undergraduate degree. Then he got a graduate degree. Now he is working on a PhD.

Along the way he met a nice girl, dated her for 2 years, and married her. They seem happy.

I think you should give him a chance. If he blows it, you can be part of his learning curve. Sure you might get hurt, but you have to participate in life to have a life.