Unlike ephedrine which is prescribed for human use, DNP is not. As a consequence, there is no 'recommended' dose. And no, don't take 1600mg ephedrine either.
As for taking 3g DNP, I wouldn't take 3mg personally. Remember, those LD50 values are for acute dosing. For chronic dosing in humans.....well this is where the bro-science comes in because they stopped the trials in the 1950's. Some people will tolerate things better than others because we're on a roughly normal distribution.
Here are some more interesting sides for this compound when dosed chronically in animals: along with marked increase in metabolism, wt loss, increased body temperature & profuse sweating, there's the nausea, vomiting, collapse then death. Can also cause cataracts, granulocytopenia, polyneuropathy & exfoliative dermatitus.
Don't let me stop you though, you have the facts, it's your life.