Most LFS will tell you a 10 gallon is big enough for a bala shark if they could get a sale out of it. They're not usually the most reliable source of information. You're better checking a site like this for species research http
/www.seriouslyfish.com/species/xiphophorus-maculatus/
To be honest I am surprised that nobody else has spoken up because usually I will quote 60L as minimum for platies and at least two people will say no, even that's too small for platies! But your heart seems already set.
You can make a decision about whether the females need a break from the male after you've observed his behaviour for a while. If he constantly hassles the females and they seem stressed then you can consider separating them, although this won't stop the females from producing babies until they run out of sperm stores.

To be honest I am surprised that nobody else has spoken up because usually I will quote 60L as minimum for platies and at least two people will say no, even that's too small for platies! But your heart seems already set.
You can make a decision about whether the females need a break from the male after you've observed his behaviour for a while. If he constantly hassles the females and they seem stressed then you can consider separating them, although this won't stop the females from producing babies until they run out of sperm stores.