I have never been a fan a vinegar because of the aroma. So I have always used Muriatic Acid. However, this is nast stuff and not for the average user as it is dangerous. We had for stain remove in our swimming pool and it works under water. I also use it to lower pH in one tank, Finally, I have bought a lot of used tanks and I do a two stage cleaning. The first is an acid wash where I use a small amount of the acid in the tank which is filled to the top with water. That removes most of the calcium build up.
However, some stubborn spot remain and for then I use a stronger solution applied using a Q-tip. Anything that wont rub off will scrape off using a single edge razor which you can buy at any hardware store. This may be your best soltuion for removing the white dots as opposed to anything acid.