Look at what the cap has been since the new CBA and where it's at now.
The percentage of pushed money is far more than what the cap is being increased.
Your model is over simplified but it doesn't really model what the Cowboys are actually doing. This year alone they are the second least spenders in the NFL because they are swallowing $25.5M of dead money that is directly related to the $20M they were over two seasons ago. That's a bigger percentage of dead money vs what the cap has risen from 2010.
They are spending $99M if the $133 cap limit. That's a huge disadvantage.
Their current spend is more than $99M because they are pushing money forward.
I'll try another example. Let's say that the dead money is 5M and Romo is the only player on the roster and the cap limit is 18M. That would "look" like this:
Cap Limit 18M
Dead 5M
18M - 5M = 13M
It appears that they are only able to spend 13M of the 18M cap limit; however, Romo's average total pay per year on his contract 17M. That indicates that they have a 17M per year player on the team with a cap limit of 18M. They are effectively using 17M of the 18M cap, not 13M. The difference between 17M and 13M is 4M which is the amount on average that is effectively being pushed forward. The previous amount had been 5M; therefore, they are operating at a sustainable rate because they reduced the push forward by 1M.
Dead Money and Push Forward are not the same. To determine money pushed forward, you take the total that the player gets paid for all years including bonuses and divide by the number of years the player is on the roster. If the player's cap hit is less than his average pay, then the difference is pushed forward into future years.
You would have to look at the total push forward amount to see if it is increasing or decreasing relative to the cap limit increase. Dead Money is just the part of push forward money for players no longer on the roster. There is some randomness in terms of how dead money occurs each year. It's the overall Push Forward amount that is critical, not the dead money portion. Romo's cap hit in 2014 is 11M but his average pay is 17M; therefore, 6M is pushed forward from his contract and that is not dead money because he is still on the roster.
FYI - The dead money was higher in 2013 than it is in 2014 and projects to be significantly lower in 2015.