re: water filter for fluoride, chlorine and calcium

Propur makes an inline filter that works well for just about everything that can be filtered. I dont think hard elements like calcium can be filtered. I think you need a softener for that.

I use a 3-stage activated carbon filter for the whole house, UV light to deactivate all the chloramines you can't filter out and then a ProPur inline at the fridge to remove the fluoride. It seems to work well for us. I replace the ProPur every 2 years.

RO is nice for under a sink/drinking spigot use but it is very wasteful and you need to add nutrients back in after going through RO. Consider it for very specific use only.