Wouldn't the bombs go off when they get chrushed (by that time the repusle and Colossus are a nice jumble of twisted metal), not when the front of the Repulse hits?
I guess that also depends on where the bombs are stored, but still. One could argue that an explosion would push part of the Repulse in front of it only harder, thereby increasing the pressure on the Collie.
And again, in the past, a ship purposely stuffed with explosives (thus far exceeding the Repulse's impromptu explosive potential) didn't do that great of damage either.
Exceeding? How do you figure that? A Aten cruiser in FS1? With what was it stuffed? The HoL was not known for powerfull warheads. and again, you're forgeting that the Repulse is like, more than a 100 times bigger. It's ordinance stocks are probably bigger than the Aten.