The cable used in a satellite system installation is usable in an OTA antenna system provided it's not damaged physically or by moisture intrusion. You would be safe to assume that most, if not all the other parts of the old satellite system will need to be completely disconnected because they often block OTA signals.
I would suggest you ground your system. I can't assume that the existing ground connection to the satellite system was effective or correct. Please see:
http://forum.tvfool.com/showthread.php?t=901 Post #20 is a summary.
The monitor output of the CM-7721 is an attenuated output, about 20 dB lower in level than the primary output. This DA is suited for small to medium sized MATV systems such as found in apartment complexes, schools and motels. With a gain of 22 dB, it's more amplifier than most single family homes would need. However, you have it, so simply leave the monitor free for connecting a test receiver. Connect the output to the input of your passive splitter.