Well in case it helps anyone else, I connected my tivo to the SAT / Antenna input/output and the tivo is now working with no problems. I connected my cable modem to the CATV / Modem input/output and saw some signal loss but not significant enough to make a difference. Average power level on my modem went from -4 to -5 db to -8 to -9 db, all of which I hear are within acceptable levels for Comcast in my area. The only major difference I can see on the admin page on my cable modem is that instead of showing all 8 channels in the downstream bonding channel value section I'm only seeing channels 2, 3, 6, 7, and 8. Upstream remained the same with only 4, 5, and 6 showing up as channels.
Either way, I did speed tests and got the same speeds whether I was directly attached or passing through the H15. If anyone knows if not showing all 8 channels is an issue, let me know. Otherwise, I suggest that any of you that have this issue to try out connecting your cable tv box through the SAT connection and your cable box through the CATV connection.
UPDATE: I had the cable modem connected to the CATV/Modem connection on the H15 and it worked ok but I found that I was dropping connection every few hours, which was unacceptable for me. I have since connected my cable modem to pass-through a smaller unit panamax M8-AV-PRO and have since had zero issues. I'm getting full signal strength as I did before. My advice, do not connect your cable modem to the H15's CATV / Modem coax connection... it has a splitter built in and you just lose too much signal strength when connected. I've considered getting a larger panamax instead but the only one I would even be able to think about is the m5300, which doesn't have voltage regulation like the H15. I'll likely keep the H15 and use something else for coax protection.