Batteries, as they are being recharged, generage hydrogen. Hydrogen is very explosive. The vent tube is to prevent the buildup of hydrogen gas.
As far as batteries go, I buy only Interstate batteries. In Colorado, the temperature can hit as low as -30F. Never had a problem.
You can't buy a battery that has too many cranking amps. Voltage is a different story, however. The starter will draw only what it needs. The more cranking amps you buy, the more cranking time you buy. Remember that at 0F a battery has only 20% of the rated capacity. Capacity is rated at 70F. 20% of 660 amps is 122 amps, the available current necessary to spin the starter at 0F. 20% of 450, or 90amps max is all that your old (age is a factor also) battery had available for spinning the engine over. At 12V, 90Amps ain't much as far as turning over a cold engine with thick oil.