Take it easy on me guys -- I'm new.
Unfortunately, I know way too much about this particular topic. To answer EMB145's questions simply, in the United States, the minimum assumed climb gradient for BOTH departures and missed approach procedures is 200 ft/NM or 3.3%.
The missed approach gradient was, until recently, thought by most to be 152 ft/NM or 2.5%; however, the FAA has changed its policy in this area.
As far as PANS-OPS goes, the departure criteria is the same, and I do not know if they've followed suit on the change to missed approach procedures or not.