Do I get cunning, physic and spirit points on the second half of my dual spec when I up the mastery bar? I went soldier and demolisionist - soldier is full up but I don’t want to waste any points in mastery if they don’t give me points.
Your misuse of the term “dual spec” annoys me. 
“Dual spec” means having a switch out overall spec in most MMO’s, such as having a Healer and DPS spec option on the same character.
Grim Dawn currently doesn’t support “dual spec” and probably never will. Your mastery combination is simply one spec that contains two masteries, it’s your only spec, and your second mastery is just that - a second mastery. Unless we’re getting into some mumbo-jumbo about the duality of the soul or something and that doesn’t make any sense anyway.
Yes, you get Physique/Cunning/Spirit points from any mastery you point points into. Your masteries are not in some sort of a primary/secondary relationship other than the one you started out first: they’re essentially equals.
But, please, don’t call it dual spec. Please.
ohhhhhhhhh