Grant:
A vacuum is a volume of space that is essentially empty of matter.
keep in mind that when you start and you look at the gauge which you are using. It is displaying a pressure of "0" which is actually the current atmospheric pressure (inside and outside the vessel) being displayed like an altimeter. On a pressure gauge you do not have a Collsman window like an altimeter, to dial in the pressure differential compared to 29.92"hg. When you pull a vacuum on a refridgeration system, you are actually removing (matter) contaminates, like oxygen, nitrogen, water (in vapor form), etc. It is better to pull a vacuum slowly to remove these contaminates. If you pull a vacuum quickly, the water vapor will evaporate and turn to ice and freeze to the container wall. Then the gas which you use as a refridgerant will be contaminated and can cause the gasses evaporation process to be hindered. A 1 to 2 cubic feet/ minute rate will work well for "moving" the contaminates out of the system. your local AWOS or FBO is a source for the current Barrometric pressure.
Example: If you are under a high pressure system and the current barometer pressure is 30.5"hg then subtract 29.92 from this to see a callibration differential of .58"hg.
I hope this makes a little sense for you.
I have never used Methanol as a refridgerant, most absorbtion refridgerators use ammonia for a pressure-equalizing fluid, butane as refrigerant, and water as an absorbing fluid.
Sorry, I got caught up in the moment...
Depending on how critical the vacuum (removal of matter) is, you might need to use a "vacuum pump" designed for operating to the lower pressures. Talk to your local HVAC guy and borrow his pump. Tell him what you are doing and he will most likely want to help, if nothing else just to see if "this thing" will work.
Good luck
ps:
most household vacuum cleaners are only about 20% effecient. The intake on a vehicle is maybe 45% efficient.. nowhere near enough to do what you want.