I am not inspired by pvc blades, I think you will be hard pushed to get much from them, that motor is a bit on the fast side. 3 blades or 4 makes little difference.

I personally wouldn't use a dc motor or pvc blades but don't let me put you off. I have been playing with wind power for a long time and passed that sort of thing many years ago. Many start that way and progress to better things or get put off with poor results.

I suspect that 1.5hp max on a treadmill motor does mean that. From the size of some of those things I can only believe it is a very short term rating and continuous it may be nearer 1/2 hp.

"Lastly as you said it can make 200W, how long will it take to charge a 12V 145AH battery. "

I doubt that you will see 200W often or for long. I can't even give you an estimate of charging time, but you would probably need to base it on 10 -20 Watts continuous.

Don't expect much any you won't be disappointed, it's not going to power a house.