The Nifty futures should theoretically be priced higher than the Nifty index. If the premium is lower than it should be, or if the futures are priced lower than the Nifty index, it could be attributed to hedging, heavy speculation, or it could just be the effect of dividends. Anyway, one shouldnt read too much into it.
Your third point is the much more interesting one. Increases/ decreases in the premium/ discount should be viewed in conjunction with the increase/ decrease in Open Interest and that will tell you quite a lot.