I may be wrong, but I think the lever is supposed to stay tight against the safety when you close the action. I don't think you should have to hold the lever fully closed to fire the gun.
For open sights I'd zero at either 75 or 100, because I wouldn't be shooting much more than that (I'd put a peepsight on it too). For a scope, I'd sight in to be around 2" high at 100.