That chart is erroneous. It doesn't account for the change in blocktime and thus erroneously shows a hashrate that is twice as high as the actual hashrate.
Damn. So on the uptick, but not as much as that chart would suggest. Is there an accurate one somewhere?
Any pool, like http://minexmr.com or http://mro.poolto.be, or an explorer like http://moneroblocks.info/ or http://minergate.com
The pools mentioned are all shitpools. If you take steep emission curve into consideration, the pool that definitely pays the most is the pool with the highest hash rate - monero.crypto-pool.fr
Nonsense. The best pool is the one with the lowest latency to your miners, lowest pool orphan rate, best reliability, reasonably-frequent but not too-frequent payouts (no more than once per day; less is probably better), and lowest fees. That won't be the same for everyone.