1- It all depends on how much filtration you may have in your tank and plants... if their waste is used up ( as ferts for plants) or filtered out quickly and broken down by the bacteria, you can generally get away with more fish. so the more plants and filtration generally will mean you can have a few more fishes than recommended, just don't go overboard and buy a few big discus
... the fish also want some space to swim around, don't overcrowd because they may feel stressed and die.
2- those plants are great for a small tank like yours and they are fairly easy to keep up with, just remember that the stargrass is very macronutrient hungry plant , which is no problem if you are using ferts, and that it grows VERY quickly, tending to grow upwars not sideways... so you will need to trim it fairly often if you are looking for a foreground coverage. Another plant you might like if you are looking for a background is very the Echinodorus vesuvius, or at least I love the looks of it, specially on smaller tanks.
3- Yes the swap and shop here is awesome.
One thing you didn't say is if you are going to be having a high or low tech... most of the plants you are planning on getting like more the High light and C02 and ferts...
The 2222 is ok, if you think it is disturbing too much the plants you can always turn it down... I'd use the 2213 if you think you may not be replacing/upgrading your tank anytime soon or the 2215 if you think you might switch out for a bigger tank ( up to 30g ) or a 2217 if you think you may end up with a 50-70g tank...
2213 $79 - 116 gph
2215 $120 - 164 gph
2217 $150 - 264 gph
2222 $160 -132 gph
I think the 221* will give you more bang for your buck... and you can always reduce the flow.