I just don't think the stand off range is sufficient for a non fighter aircraft to survive the delivery in that close a proximity to the mainland.
Well, the B-1B could be used for that purpose - they could do low-altitude approach & toss delivery, then making supersonic retreat.
Never saw the Bone doing tosses with J-series weapons, but lots of level deliveries, some from zoom climb pop ups. I conducted a level one from .94M at 1500 ft AGL and Mk65 mine drops from the BUFF. Problem here is the bay door limit of .94M and it's poor performance at altitude.
Honestly, if you want to mine the harbors close to the mainland Bones and BUFF's aren't the platforms to use unless you add propulsion to the glide kit. Go with B-2's, B-21's or better yet submarines, the latter being the best option.