I think it was a useful lesson in learning the business. I understand where you're coming from but from the writer's perspective, you started offering him large sums of money which in all reality would never materialize. Instead of helping to educate you and work with you, he sought to let you find out the hard way. Honestly, I think it's good that you learn to write a screenplay so you're in a better position to evaluate future scripts as producer and director.
Given the financial constraints, it would be better to think in terms of a short film initially. There are so many possibilities with today's technology. People make awesome shorts using just their iPhones. Check out this episode of Film Riot (
https://www.youtube.com/watch?v=Ptz_ybNRavg).
Short films can be great ways to get noticed (YouTube, Vimeo, etc.) and learn about film techniques as a background for that feature. Shorts don't take a long to write, don't require as much to make and can be great opportunities for networking with others also interested in filmmaking.
Do read some books or check resources online about formatting and script writing. I find it's easier to write up the whole story first. This summary or treatment gives you a solid basis to convert into a script. As Daniel pointed out, there is a structure that helps guide development. As a rough guide, the first act is 25% of the script, the second act which is the meat of the action is about 50%-60% and the third act wraps up the package and is 15%-20%. It's important to remember that film is predominantly a audiovisual experience. The role of the script is to develop character and layout story and action. It is a blueprint for the film. A well formatted script can help with budgeting, scheduling as a production tool.
I know you have your major film idea. Try starting with a smaller project to gain some experience. If you've never directed or been on a movie set, volunteer on other people's projects. One, you'll learn something. Two, you start making contacts. Three, you have fun.
Good luck.