As for enabling ssh on your Steam Link its very easy. All you need to do is get a pendrive and make this file in these folders: /steamlink/config/system/enable_ssh.txt (Note: the file must have some data in it, if enable_ssh.txt is empty it will not work)Source
Then reboot the Steam Link with the pendrive inserted, after its done connecting to the network you can ssh into the Steam Link as root with the password 'steamlink123'
Also, here's how to set a new bandwidth limit (which can be higher than the limit in the GUI):
As you know, you can set "30Mbps" as the highest bitrate in the steam client settings. "Unlimited" does not work with HW acceleration enabled. So what you have to do is manually edit the steam settings file in any text editor and set the bit rate to any desired value. I've set it to 100000 (100Mbits) and it works great, real stream bitrate is around 80 Mbits and video quality is GREAT.Source
Steam setting file can be found in:
"c:\Program Files (x86)\Steam\userdata\xxxxx\config\localconfig.vdf"
and the value you have to change is called "BandwidthLimitKBit" "100000" (for 100Mbits).
So close the steam app, find your settings file, change it, launch steam and enjoy the high quality streaming again.