Yes, I've seen those references for the "blue light". They don't reveal much except somebody else from that period heard about the "blue light". There is nothing that illuminates (no pun intended) just exactly what was the agreed to signal and what exactly would distingush Dixon's signal from any other ship in the area that also used blue light signals-- (two blue lights means Dixon really had his hands full).
The weight of the hunley is not the issue when submerged is this case, since the whole idea was to become almost weightless. The issue is center of gravity which is changed when adding another twenty feet of length adding in the weight of the spar and 60-150 pounds of the torpedo at the very end. Even more modern submarines from World War I and World War II would buck and bounce when firing a torpedo, but they could recover faster because of compressed air and motorized pumps.
Even if the Hunley could recover trim quickly after planting the torpedo on the target, this meant either the rear man would have to pump out an equal amount of water or Dixon would have to pump in an equal amount of water weight or both men working together would have to recover the trim pumping water in and out...while they were supposed to be backing away during the most critical part of the attack; the dive planes would only have added a complex manuver in trying to recover trim, and only would have effected the depth of the Hunley, not the trim, but Dixon was either stearing, pumping water or controlling the dive planes- he couldn't do it all at once- which made control very awkward and slow.
Do you know why the men of the Hunley brought their hats? So when they used the snorkel to draw in air near the surface they would fan their hats to creat air flow, so they could breath...again taking their hands from the power of the shaft to perform a needed task.
Again, testing and simulating this would be a great boon to our knowledge of events.