Well hashish is pretty much all the THC from cannabis buds, compacted down into a smaller portion, making those smaller portions much more potent, so yes, pure hashish is much more potent then the actual buds.

1. Yes.
2. Depends on what method you use. For dry sieving though, all you need is some slik screening and a makeshift shaker.
3. Depends. If you have high quality, good tasting smoke, then I wouldn't bother. Hash is usually made from left overs from harvest times from plant matter than is not smokeable. Use mids or low quality to make hash and save the good stuff for smoking.
4. Yes, if made properly.
5. Yes.