I am new to SEO. Could you please help me?

1. I like to post programming tutorials to both my website & various programming forums. Is that going to screw up my website's ranking in Google?

2. My editor of my history website who sometimes posts essays there also posts them in some history forums. Is that bad for SEO?

3. I made a Facebook page for my history website. It says there "Promote your page" basically you pay $5 for around 100 likes. Has anyone tried that? Does it work? Because $5 seems like little money for additional 100 likes which will increase the traffic considerably.

Thank you so much for the help!