An E-spillway is a must, and you got the idea right....the level of the E-spillway should be about 6"- to a foot above the top of your primary drain, slope AWAY from the dam slowly, and be at least 15 feet wide and well vegetated to prevent erosion/washout if used.
As for your drain pipe.....2 ways to fix it...pull out the rip-rap, re-grade and compact the eroded soil in a curved shape to channel the water, then put down heavy plastic or geotextile fabric and re-lay the rip-rap....this will eventually fail again years later.......best way is to pour a quality, concrete tail race, also in a channeled shape with rip rap on the edges to help keep water on the concrete.
As for the pond side of your pond, check out PondDamPiping.com and get the correct sze trash rack to prevent blockages
