Bell is full of shit that it doesn't support faster speeds... It's just a question of setting the sync rate... There is a 45/9meg FibeTV profile..
As for your upload speed, it's probably a profile error. I'm sure someone in the direct forum can check it for you.
And yes, the downloads get slower as you watch TV. it's a shared resource from your total sync rate. As you watch tv (or are recording to the PVR if you have one) the speeds get slower.
Which is exactly why they should be setting the sync rate higher, but whatever Bell... How are you dealing with the low caps?