Yeah there's only one splitter (it's 5-1000mhz), this a picture of how it's connected:
http://i.imgur.com/is968mc.jpg - The modem cable is the bottom right one and the TV one is the bottom left one.
So the modem downstream affects the TV as well?
Well the TV and modem would have the same specs if they had similar cable conditions. The modem wouldn't really cause anything with the TV but they're both probably getting the same signals if they were hooked up to the same thing.
Your TV is going to have a 7dB drop and your modem will have a 3.5dB drop in signal with downstream power level and increase with upstream based off the ports on the splitter if I'm correct.
How much longer till Comcast comes?
Even if you remove the splitter you would still have okish signals but your upstream would be near the high end but would be the "Good enough" zone.
When the person comes you should ask if they have any splitters on them because they usually carry the high quality ones.
Do you rent your modem? Should also see if they could upgrade you to a Docsis 3 modem while they're there if you're renting.
If you're not renting I suggest you upgrade to a Docsis 3 modem as Comcast will soon be putting Docsis 2 modems as "End of life"
Here is a modem to buy if you're not currently renting a modem or have Xfinity Voice: