My Adsense earnings are often very low so unforutunately I can't confirm. Anything for me is better than nothing I suppose
Generally the reason for a sudden drop with no valid obvious reason like a weekend could be a problem with your hosting server. The same happened to me twice and it turned out to be the hosting server problem. Keep a watch on them too as they might cause issues. If you are earning well, go for dedicated hosting!
Well if your site is regularly updated with high traffic then you will feel increase in your earnings