If you supposed to get a 10000kbps connection, you would be receiving more than 960down tweaked or not. Cablenut settings will not affect the download that much.
You know what try this and see what happens
DefaultReceiveWindow = 1280000
DefaultSendWindow = 163840
DisableAddressSharing = 1
InitialLargeBufferCount = 200
InitialMediumBufferCount = 480
InitialSmallBufferCount = 640
LargeBufferSize = 819200
MaxFastTransmit = 64000
MediumBufferSize = 150400
PriorityBoost = 0
SmallBufferSize = 12800
TransmitWorker = 32
FastSendDatagramThreshold = 4096
EnableFastRouteLookup = 1
EnablePMTUDiscovery = 1
IgnorePushBitsOnReceive = 0
GlobalMaxTcpWindowSize = 513920
MaxFreeTcbs = 8000
MaxHashTableSize = 16384
MaxNormLookupMemory = 5000000
SackOpts = 1
SynAttackProtect = 1
Tcp1323Opts = 1
TcpLogLevel = 1
TcpMaxDupAcks = 3
TcpMaxHalfOpen = 100
TcpMaxHalfRetried = 80
TcpRecvSegmentSize = 1460
TcpSendSegmentSize = 1460
TcpTimedWaitDelay = 30
TcpUseRFC1122UrgentPointer = 0
TcpWindowSize = 513920
MaxConnectionsPer1_0Server = 20
MaxConnectionsPerServer = 10
DefaultTTL = 64
DisableUserTOSSetting = 0
TcpMaxDataRetransmissions = 6
DefaultTOSValue = 90