I will probably not use vermiculite in the future. It was part of my mix for years but with the new soils that are available (eg Fox Farms) there's really not much need to make your own mix. Fox Farms (or whomever's pot soil) and a little extra perlite to taste and you have pretty much everything you need. I was reading the bag yesterday and it even has dolomite lime in it already.
It's pretty much an eyeball thing, but from 30% to 40% with the perlite.
If it looks like you have too much, it's just right.
Yes, FF does have dolomite in it. Just not enough for the entire grow. It's really kinda hard to over apply lime. The extra Ca does a world of good. I use a healthy cup of dolo/cf AND a cup of gypsum for more Ca and the sulfur.
Gypsum doesn't affect pH, so don't try and sub it for lime.
Can't comment on FF or any bagged mix for that matter, I have been making my own for just over 40 years. Just never saw the need when I could do it much better and way cheaper.