Your DM is sticking too close to his plan. Ask him as nicely as possible if he can improvise now and then. The numbers only matter to the most hardcore of players. You have to get a sense for die rolls and just go from there to keep the game moving. Is the door made of oak? Kicking it down will probably require a higher roll than if it was rotted through. Maybe only a Warrior-type character can do it. Is a character trying to slash a goblin in a super narrow hallway with a longsword? Probably a difficult throw. Is your character a thief trying to eavesdrop on the other side of a hollow wall? Probably an easy throw.
This is my problem with published campaigns generally, I think. I much prefer when a DM has constructed their own world not only because it's more interesting, but also because it allows for greater and more effective improvisation. It seems to me the best improvisation carries with it the necessary underpinning of a fundamental understanding of the world in (or with) which one is improvising, which is easiest to obtain when it's a world you've constructed.