I answered to your questions below!
I lower my price because here at freelancer i am starting, fair isn´t it? I work with Facebook pages with more than 5 k followers. I am a bachelor at communication advertisement and i look for specific targets for specific marketing campaigns, this work thrills me. I am passionate about it. I aim at psychological profiles, what people like to do, what people think, what makes them buy your specific product or service. I have more than 10 years experience in digital marketing, web development and creative work. Enough about me. I want to know what do you need, what is your passion, your dream. Contact me so we can talk. Looking forward to work with you! If you need more information about me or my services please fell free to contact me anytime.
Answering your questions:
The best is: starting pre-launch and continuing into post-launch. This is well know strategy for most products or services. You can see teasers for games, series, movies and so on.
I estimate that for 50 dollars well invested (that is my job) you can get 1 thousand followers in one month. But if your product or service is popular, it can be more ( a game for example). If it is something not so popular, let´s say a technical book, then it can take longer.
4. About 1 month for 1 thousand followers.
Example: facebook Constos sucintos 5k followers. It´s about short stories, not so popular in Brazil.