You could try goosing it with a ten amp charger for 15-30 minutes. Make sure it's in a safe place if it vents. If the charge meter indicates maximum charge for more than 15 minutes, the battery is shorted. I'm guessing your battery is shot, although you might double check the charger, too. MC batteries aren't as reliable as car batteries.
It sounds like you have problems with several cells. I am not sure if anything will work.
We used to revive weak batteries (8-10 volts) by putting 1/2 teaspoon of Epsom salt in each cell, then charging overnight. This method seems to dissolve some contamination on the plates, but only works for about one year. After that, the battery is completely dead.