This "instant cycle" bottles don't work. Bacteria cannot survive in those bottles.
You can cycle with your fish in the tank as mentioned, it will just take longer because you need to make more water changes to avoid ammonia or nitrate poisoning.
You can definitely make a knot in the tubbing to adjust the air flow... it's the same concept of a valve, stopping air from passing through the tube. I ran pumps like that for a long time and no problems.
Now, the benefit of a valve? You can hook up many tanks ro one pump and you don't ruin your tubbing.
Currently I have 3 tanks running on one pump and I'm sure it would support another filter if I had the shelve space.
I agree on investing on a sponge filter... it will give you the water circulation/aeration you're looking for, grow befenicial bacteria, and be gentle on your fish's fins.
I would not add any airstone to the filter or tank, the filter will give you plenty water movement and you don't want a strong current in the tank.
These are the filters I use: http://www.drsfostersmith.com/produc...54&pcatid=3954
very economic but you can always build your own.. they are quite simple to make. The filters in the second link have a heavy base which i quite like.
You can match the filter to your tank size, over filtering with sponges is no problem... I have a 30 galon filter in a 14 galon tank and another 25 galon filter in a 2.5 galon tank. It just gives you more surface to grow beneficial bacteris. But you want to make sure you look at the dimensions and check if it will fit in your tank and youre ok with the space it will ocupy.