You should distinguish more clearly a deficit in the flows to one in the balance. As you note later, 2015 is a deficit in terms of flows -- expenses exceed income. The Fund has a positive balance till 2030-something. In principle, it is only then that revenues or benefits would need to be changed to finance the program. (You won't find it in the Actuaries reports, but the Unified Budget is projected to have enough revenues to supplement the Trust Fund, without going into deficit, until 2050.)
The Center on Budget and Policy Priorities has put out papers quantifying the effect of the 2% carve-out on the Trust Fund. The author is Peter Orszag. Recommended.
As I've said before, it would be giving away too much to call the Bush prop a "plan."
mbs