You should actually spread your intake of water through out the day as opposed to putting it all away at one time. There is no evidence to say that drinking water at night has anything to do with specifically putting on weight.
Your second question may not be answered until one sees you actually doing the kapalbharti and checking to see where you are going wrong.
If you add muscular strength to your routine as you should, then you may add kilos to your weight but will not be able to tell unless you do a body composition analysis, to determine what percentage of fat, water and lean mass your body is broken into. Muscles weigh more than fat but take up less space, in the body.