No this doesn't seem right, are you sure you're calibrating the meter correctly each and every-time you use it? You must calibrate it each time you change scales. When you measure the impedance of the speaker lines, you have them disconnected from the amplifier, correct?
In 10 years of working on paging systems, I can't say I ever used anything other than 1X...not sure why you're using the 10X mode...
Are you sure this is a 70V system? Where are the speaker terminals landed on the amplifier? Have you checked the system for ground faults? Just because paging works does not mean the amplifier is not overloaded.
To answer the original question, you could probably just feed the TOA amp and the Valcom paging adapter from the same Algo output, as the TOA amp has a high impedance input (provided of course it is connected and configured properly as a line level output). It really sounds like you are in over your head though. My suggestion is to use only 70V speakers and forget the Valcom. No sense in having two systems to accomplish the same thing...
