I don't know the answer to all of those questions. DNP is an insectiside. If you read the spec sheets on it you'll see the negative side effects listed as the ones dieters take it for! Try a couple web searches.
An overdose is fatal and taking insectiside for long periods is obviously not easy on your body. I wouldn't use the stuff as an answer to a poor diet.
Consensus seems to be that a long-term cycle at 2-400mg per day for 3 weeks on/2 off is good. I'd probably use an ECA stack on the 2 off weeks.