Alarm drawing too much power

So I finally got my Scytek 4000RS installed (except the remote start).  Everything seemed to work fine, except I'm having a few problems.  The vehicle is a 98 Blazer 2door.

-Battery died from 5 days of not running the car.  It seems like the alarm might be drawing alot of power somehow.   I pulled the alarm fuse & hooked up my multimeter connecting where the fuse was & it was showing .1 volts.  Is this normal?  How do I trouble shoot this issue?

-What is the purpose of the diode running across the starter kill relay? I placed a diode across it (yes the diode polarity is correct) but I think the diode might be fried... could this be causing the battery draining mentioned above?

-Also... does it matter how I mount the 2way alarm antenna?  I currently have it mounted upside down.  Does this matter as long as the antenna mast is perpendicular to the ground?

Thanks