Good calls, Broke but I'll add from my readings that then Defense Secretary Robert McNamara who strongarmed his "TFX" F-111 through development was also the biggest champion of the FB
-111 bomber variant. The Air Force really wanted the AMSA (Advanced Manned Strategic Aircraft), which became the B1-A but development and budgetary delays led to ordering the FB
-111A as an interim medium bomber to augment the B-52 while the B1 was developed. The order was severely cutailed from about 250 airplanes to around 78 because the FB
-111A was severely limited in ordinance by it's small size. A later proposed stretched FB
-111H was also axed because it was still too small compared to the B-1A, though a lot cheaper to develop. You're dead on about the B-58, amazing as it was for its' time. The hot, nearly 200 mph landing speeds also helped make it a dangerous aircraft with a high attrition rate, as B741 said, though the FB
-111A, like its' fighter breathren, was hardly much better.