What are my chances of becoming a pro skateboarder?

You will never go pro, sorry to say so. You could get a flow sponsorship in about 10 years of skating if you keep with it and improve fast. I have been skating for nearly 8 years now, and I am working on getting flow for Bacon Skateboards and Vox footwear. I am 17 and have a 0% chance of going pro. Pros can do huge gaps that I wouldn't even consider trying myself.