I wanted to grow Cocoa, but I couldn't get my hands on vital seeds. The problem is that those seeds lose their vitality incredibly fast. There are also types wth more cocoa inside and less cocoa inside. An acquintance of mine from Brazil grows some cultivar of Theobroma, but not cocoa, he says there's at least 5 times more cocoa inside the ripe fruit. Maybe worth a survey?
I also second that humidity, if you expose Theobroma cocoa to dry climate, it will soon perish. The only plant I've ever seen with my eyes died from insufficient air humidity before it fruited.
Good luck!