You say "masks", but you actually include social distancing and all the associated problems it causes economically and emotionally. Then you compare it to a vaccine. I can't take your argument seriously. As I have stated many times, I wear a mask when I am going to be around people, but it's a virus. People wear low-value masks and don't always wear them - including our leaders. If that's not part of the equation, you aren't living in the real world. You don't have to wear a vaccine properly and socially distance for a vaccine to work. Enjoy using math to mislead people.
You've forgotten the vaccine comparison came when we didn't know if any vaccine would reach 70%.
The 70% estimate is from the real world. It is 70%, as used in the real world.
Errors in fit, behavior adaptations, and so on are real concerns, but they are already baked into the 70% estimate.
Grace's point about in home transmission makes a bigger difference. The vaccine gets its full power in that setting, but masks and distance get nothing.
In some sense, it means any vaccine reduction should get counted twice. In a chain of 2 transmissions, one at home and one outside, the vaccine reduces both. So a 70% effective vaccine reduces the chain to 9% of what it would have been. (.3*.3).
Similarly, a behavior change reduction should get counted once. A 70% effective behavior change reduces the chain to 30% what it would have been.(.3*1)
In effect, a 70% effective mask is similar to a 45% effective vaccine. Not as good as J&J, but not zero, either.