So the vinegar will dissolve the calcium stone THROUGH THE SKIN???
Not from the outside, but from the inside. The glands have small openings where the saliva can pass. This is where you want to focus so the acid can get in to the gland and dissolve the stone. Depending on which of the glands is being affected you may be able to gargle with the vinegar to get the acid to the glands while keeping it away from the teeth.
I can easily do what you recommend. I love vinegar. :)
Anything I can do to prevent these from forming in the first place?
A couple of suggestions, but I cannot say for sure if they will work. Nettle leaf and magnesium malate or malic acid can be used to dissolve stones in other parts of the body, so they may also work in the salivary glands. They are all beneficial to the body, so even if it does not dissolve the stones they will still provide other benefits.