Not to rain on your parade. Your numbers may be right for savings, but your logic is flawed.
Yes, Cutting EJ will save 2.8 million over 2 years.
Cutting Cassel will save 4.15 million for 2015 and additionally 4.15 will be available for 2016 as it is not tied to anything
So:
If you cut EJ and keep Cassel this year and next year at ~3 Mil; its a savings of 3.95 Million over 2 years.
If you cut EJ, and keep Cassel just for this year, its a savings of 6.95 Million over 2 years (Minus whatever you have to pay a backup QB...~1-3 MIL)
So say savings of 4.95 Mil (assuming 2 Mil for the year for backup QB)
If you cut Cassel, but keep EJ, its a savings of 8.3 Million over 2 years
Cutting Cassel is a 3+ Million better option from my point of view.