Max Sealevel Speed
I happened to be researching this subject when I came upon your site. I believe the term you are looking for is "Q-Limit" or the dynamic air pressure the aircraft structure is designed to withstand. Comparative information seems to be hard to find, but it appears that the F-111 and the B-1A both had Q-Limits of Mach 1.2. I can attest to the former having flown the fighter models (A & E) of the F-111 for 18 years and that included a very memorable Red Flag mission when my wingman and I "got out of Dodge" doing mach 1.2+ at 300' AGL (about 3000 MSL) and we were not in full afterburner. As for a ram jet effect at high mach, this was definitely a characteristic of the F-111. As an FCF (maintenance test flight) pilot at RAF Upper Heyford in the 1970's we always took the aircraft to max speed at high altitude out over the Irish Sea. Typically the "REDUCE SPEED" warning light (skin heating limit) would come on at mach 2.4+ but the airplane was still accelerating. We always figured it was due to a ram jet effect with the fan duct.