When the trouble shooting gets tough, start at the beginning... In this case, the antenna. You need to prove that you have usable signal at the antenna. If you do, then move on to prove cable and splitters good or bad. Start at the beginning, test, then move down the line, test again.
Even if it requires a trip to the store, get a known good coax, 50' or less in length. In a recent post in another thread, you indicated you have an HDHR tuner. That, and the HDHomeRun Config (GUI) application (screen shots of the application here:
http://forum.tvfool.com/showthread.php?t=820) on your computer gives you a very capable signal strength and quality meter that can be tuned to any real channel without scanning. With this test set up, you can determine, with reasonable certainty, the relative quality of any signal received by the antenna.
I believe the larger HD7082P suggested by teleview early in this thread was appropriate. The HD7084 and HD8200U would not be overkill IMO. Sadly, though the C2-V is a very good antenna product, it's not got the gain and directivity that your situation calls for.
You have steep terrain blocking your path. You need gain and directivity to overcome that. Also, older ATSC tuners have less ability to compensate for the effects of multipath interference. The larger antennas tend to help by receiving more signal from one direction, while receiving less from the rest.