Now if you have the Gold or Platinum plan, reducing the resolution may allow you to stream on more than one device simultaneously but, on Bronze or Silver, I wouldn't even attempt it. That''s how it works.
The top speed is for browsing and file transfers, speed are reduce for video streaming to force sites to send the lower resolution video (except on a Platinum plan.) That is intentional, it's how the plans are intended to work.
I also wonder how you are going through so much data. We run both Roku's every evening all evening and almost make it through each month, plus have one gamer who games all day every day.
Make sure your kid is doing YouTube at 360 kbps if on a small screen. That will save a ton of data. If he is now doing HD, it will eat it up for no real gain on a small screen.
Q: Will the video quality available with the service plan I purchased apply to each device in my home or do I need to share that video quality amongst all my devices?
A: The video quality for your service plan will apply to each device in your home.
Video stream throttling is applied on a per video basis. However, overall bandwdth is shared by all devices accessing the household's internet connection and each device's video is pulled from the household's shared bandwidth. The same would apply to streaming multiple videos on the same device simultaneously (although the audio experience might not be "optimized").
Once loads are balanced across what are now two satellites (more if you count the older satellite(s) that are still in use), things should be improving right where you are. Even some known, Wildblue-1 users are seeing better speeds (some well above the old 5 Mbps limit during off hours) as bandwidth frees up - more than likely due to subscriber attrition after more years of pain than we've endured on Viasat-1; possibly due to airline services being shifted to Viasat-2 in those areas; at the same time Unlimited 12 Mbps plans are starting to show up in those augmented areas as well.
Going forward the only real way to determine which satellite your on would be to position yourself behind the dish and see where it's pointing (different from whre the TRIA's arm is pointing - the dish is the collector) :
Don't worry, Wildblue-1 is not in danger of clipping Viasat-1 it just seems that way just Zoom In - only George Clooney poses that risk but I think he's still in LEO at last check ;)