Hi,
Let's start with the shorter answers :
2) It is 54Mbps of transmit speed of data frames. You need to count to overhead of signaling and the fact that wireless is half-duplex. In reality you should observe around 20Mbps of real downloading throughput on a 1131.
3) That sounds like Windows saying "limited or no connectivity" ? It means there is no route/gateway
1) You should make sure that the video is sent with the right Video QoS tag, you should also make sure that your network is correctly preserving tags for QoS and that your WLC is correctly configured for QoS.
WLC steps involve : enabling WMM, turning the WLAN to Gold quality, configuring 802.1p tag on the QoS profile.