The totals are not explicitly set out in the law, rather they are determined by the parameters set out in several sections of PUBLIC LAW 112–95—FEB. 14, 2012 and the CFR [14 C.F.R. § 93.123, 49 U.S.C. § 41718(c)(2)(A)(ii), 49 U.S.C. § 41714(d)(1)] as well as FAA implementing policies that sets out the number of operations authorized per hour per size of aircraft.

But after the 2012 changes, it works out like this:
TYPE of Op Max slots (T.O/landing) allowed per hour
Air carrier 37
Commuter ops 11
GA and unscheduled 12
Exemptions 5
Slides 2

Except for a few peak hours DCA does not come close to using all 67 ops per hour so there is room. In addition, for a variety of reasons most of the hourly GA slots are not used.

Agreed, gates are pretty busy, but I do not believe they are at capacity. I will check with people I know there. The new terminal due to open in several years will further alleviate this.

That is true, but it is only a portion of surplus revenue from DCA that can go and I believe is capped at $40 million. Significant to be sure, but not game changing. I did misstate something though - such revenue sharing also has to be approved by the airlines that use the airports, not only Congress.