1. If it is under reporting, don't worry about it. No charges are being based on the data yet anyways.
2. You can get a 2 way amp. The gateway would also work, as the signal is sent to the gateway at the entry point to the home, it then encodes the video as MPEG4 and broadcasts it to the portals via an in-home MoCA network overlaid on your coax at frequencies above 1GHz. This is then filtered from leaving your home. MoCA uses a pretty strong signal in my testing, so as long as the cabling in your home is half decent this could solve your problem. The installer would also be responsible for ensuring your gateway had acceptable levels.
3. You don't need to purchase extra bandwidth right now as the bump up program isn't yet in effect. BB50 would get you extra speed, and I love BB50, but if you don't want the speed don't worry about this yet.