it's actually fairly simple. The express 384 package works as follows. You purchase a 384kbps uncapped product which they unlimit to your maximum line speed at 8 pm and then relimit it to 384kbps at 8am (weekends run at maximum line speed from friday night 8pm to monday morning 8am). If however you have used more than 5GB of bandwidth over the past 10 days they will relimit you to 192kbps during the day and not 384kbps. You won't be informed when you are limited as it is being limited per the contract and is not a "special circumstance" limiting because you are abusing or anything. You have to remember one thing with the express 384kbps products from axxess, it is not an uncapped 4mbps product, it is an uncapped 384 kbps product with a threshold that applies during peak hours and a "bonus" speed boost at night. Your speed test is perfectly normal for that time of day on that product with a cumulative bandwidth of more than 5GB over less than 10 days.
In your response to your youtube video, when did it buffer faster, was it before you were throttled to 192 or after because some youtube videos will still play faster than they buffer at 384kbps (rare, but can happen).
Run another speed test at 8pm and you will see that you get much faster speeds. Another factor that could play a part in your slow speeds is line noise and attenuation, but it really doesn't seem like that is a problem in this case unless you are getting sub 2mbps speeds after hours, which you aren't.
edit:
Just an additional thought that I had, not sure if you know this, but 192 kbps is aproximately 0.18mbps so your 0.13mbps during peak hours is within "acceptable" ranges when taking into account overheads and shaping that may be going on.
