First off welcome to mining! I personally think you've made a wise choice mining Aeon... lots of potential for future value increases, especially with the upcoming rebase code release early April. When they do release this rebase, you'll need to update your xmr-stak miner with the latest one on github. They are making slight changes to the cryptonight algorithm to combat against ASIC miners. I'd follow their discussions on reddit.com/r/aeon
The hashrate reported by stak miner is your actual hashrate and it remains (mostly) constant, so long as nothing else starts taking away CPU (or GPU) power. The hashrate reported on the pool is an estimation based off of your miners submitted shares (and H/s.) Latency between your miners and the pool node, pool node and backend pool server and finally back to your web browser is what causes you to see fluctuating hashrate on the pool.
As far as how much you make, there is a factor of luck, network difficulty changes, pool fee (among other factors) that impacts how much you'll make on any particular day. Sometimes you have good days, sometimes you don't... but if you stick with mining this all evens out over the long run and you should get pretty close to the amount estimated by the calculator.