The F/A-18 was never in competition with the F-15 WRT the Air Force. It was mandated by congress for the navy to replace the high cost f-14 with something more reasonable costwise. It's true that the F/A-18 was competing with a navalized version of the F-15 but cost factors and the lack of organic multirole made the navalized version of the F-15 unfeasible.

The F-16 did not conform to what Boyd wanted out of a combat aircraft, execpt for the lightweight part. The F-16 has a RADAR, BVR, and while designed as an air superiority it has exceeded expectations as a multirole platform.

No, the F-17 and the F-16 were both part of the LWF (Lightweight Fighter) project. When the F-16 beat out the F-17, the USN decided to pursue the F-17 which became the F-18.