MDMA {(Methylenedioxymethylamphetamine) Molly, Ecstasy} is considered relatively safe when compared to say. hard drugs like Cocaine or Heroin. Especially when you consume the substance in reasonalbe amounts like you have described. A lot of the deaths that have made it into the media regarding MDMA or like substances, have been due to "side"-reactions like water intoxication. People are aware that hydration is wicked important when dancing and rolling, so they sometimes end up consuming too much, leading to an electrolyte imbalance, further leading to a swollen brain.
Just be smart. Stay hydrated, but don't overhydrate. Keep alcohol use as low as possible. It's healthier and will make the comedown less uncomfortable. Really, I think you have the right idea. You're thinking very conservatively in fact. Good luck with your experimentation. The one variable that you always must be aware of, is that you might not actually receive MDMA when you purchase Molly powder or Ecstasy tablets.