I should probably call my dear personal friends at Time Warner about this....
Your advice makes sense, kemist, but all the cables in question are in the walls... And I'm not interested in adding drywall to the project.
Thanks for the advice everybody! I'll futz around with putting my booster on the line between the 2-way and the TV Tuner card. If that doesn't do it, I'll make a lovely appointment for between 10 and 2...