No problem in splitting your cable, but I would run all wires from the entry point, that way if in the future you want better or more services from videotron, the signal can be directed properly, meaning that modems and digital services require less signal loss with regards to the signals at the pole. If you split else where in your house, you may end up with a series split, which means down the line you will have split after split. There is more control and more flexibility with all cables ran to one central point. With the mac address from your modem, I can check your signal strength before and after you split. Yes, you should use a good quality splitter. The one furnished by Videotron is a good one, so, use that to split to your modem, then use others to split for your tvs. A poor quality splitter will have local pick up, meaning it will pick up signals from the air, causing fantom images on channels 2, 6, 10, 12 and 17 more so for the first two. Local pick up may also cause uncorr for your modem, resulting in packets lost. Not a huge factor, but still reducing the performance of your connection.