The shop "keeping fish at a certain hardness so they'll be OK in yours" is a myth.
Fish have evolved over many thousands of years, and tank bred for only a few decades. It takes longer than a few decades to change what evolution has spent so long achieving. Having said that, commercial breeding will select for those individuals which can cope with parameters outside their native water. The fry that can't cope will die leaving those that can cope for future breeding.
It doesn't matter what the shop's water is like, it is the water where the fish were bred that is important. For commercially raised fish, this is the fish farm; for wild caught fish it is their native water. We can never know what the water parameters at fish farms are.
Looking at your list:
Celestial pearl danios hardness 5 to 15, so fine
Honey gouramis 2 to 15 so fine
Corydoras trilineatus 1 to 12, so right on the edge
Bolivian ram 1 to 10, so your water is slightly too hard.
Shrimps will also be fine, but be aware that amanos, being largish shrimps, can intimidate smaller species.
One thing you could do is to use some reverse osmosis water. This is water that has had all dissolved things removed. You can buy it from fish shops or get the equipment to make your own. Unlike pH, hardness is a linear scale, which means if you use half tap water and half RO, the hardness will be halved. In your case you would only need to use about 10 to 15% RO. But you would have to use this mix at every single water change, for ever, and would add an extra cost over the years.
Are you absolutely set on Bolivian rams? Apistogramma cacatuoides, the cockatoo cichlid, and A. borelli are fine in hardness up to 15 ppm. And these fish can be kept as harems with 1 male, several females. They just need one cave per female plus one extra to give them some choice. A cave can be anything from a natural rock with a hole, to plastic caves to upturned terracotta flowerpots with a hole in the rim.
If you really do want Bolivians, they are very hard to sex until they start to breed. And they must choose their own partners. I can let you know what to look for which while not guaranteed will help in choosing a bonded pair.
And in the size tank yours is, I'd go for 20 celestial pearl danios
