To reduce the filter flow, what would be some safe household items to use? Anything that won't decompose in, or toxify, the water. I'm sure I can find a way to make it work(with whatever I have to work with)
Online I read that 
too much flaring is a problem for bettas; is this true? If so, is separation really necessary? I think that with their continuous flaring they will build muscle and color(for the lady fish, and to swim with more ease against the filter current). They also display their full fins which I think is enjoyable to watch
Is it okay for them to constantly be on the move?
Another question: would you suggest the my fun fish tank? For those of you who don't know what it is, it's a vase with an empty bottom, connected to a pipe, connected to a spout. Gravity brings down the fish's waste, and when you pour water into the vase, dirty water comes out of the spout. I question it's cleanliness, because all it does is push out some dirt that sinks. To keep the vase cleaner, I can always do weekly washes, use plants, only give the fish enough food it can eat in a few minutes, and/or add good bacteria. So I'm not sure if it's a good setup or not, but it is cheap and it flushes a lot of fish waste out. You can even put a little plant under the spout to use the wastewater as fertilizer^-^ I say if you make sure your fish is good, do it. If you'd rather put the fish in there, over feed it and only change the water once a week, get a more elaborate and safe setup.