your temp fluctuations worry me.
they really need to be kept constant and 70 is too low.
you could get an acrylic "goldfish" tank from any petstore, around 4 US gallons which is fine.
this way you can get a 25watt heater to fit in (difficult in a round bowl) and keep the water temp regular.
as your used to doing regular water changes, you won't need a filter really, if he has water movement it can get upsetting for them, especially after they've got used to nice still water.
bettas don't like temperature fluctuations.
also i would use water conditioner by default. your water may seem fine, but there may be some chlorine or other unwanted things in the water that could affect the fish.
if he's sitting in the flower though, thats fine, those tails are heavy after all!