If you do not want the females insemenated (which can lead to upwards of 6 months of recurring pregnancy) then you should seperate them as soon as you are sure of gender.
I agree on the male and female betta needing seperated, because the male will usually kill the females when they aren't ready to breed. Multiple female bettas in the same tank will eventually begin to fight and will cause problems also.
The tetras should be kept in numbers of 5-6 of each or higher (which is entirely too many for your tank) to be content and show proper schooling behavior. When schooling fish are kept in solitary or low numbers they tend to be nervous and die sooner than those that have decent sized schools to be more comfortable.
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