You still need to provide additional information, specifically a link to your TVFool plot and you need to indicated the aiming direction of your antenna. Is it the C2 or the C2V (With VHF dipole)? What is out in front of the antenna (trees, buildings, etc)?
Spending money on a splitter with a higher frequency rating isn't money spent for any benefit, TV reception doesn't use anything above 698 MHz.
It would also hep tremendously if you specifically identified the amplifier you did use. Sometimes, amps are horribly matched to a given location and cause new problems. This isn't an amplifier problem, it's an amplifier selection problem. Sometimes it is due to being hooked up wrong, especially if you plant a splitter between the amp and its power source.