1. No point being able to change the SNR with Sky BB because the speed is capped based on the results of DLM so changing the SNR to increase the speed doesn't work. A lot of exchanges have switched from PPPoA to MER so I guess the Speedtouch wouldn't work anyway.
Some people have requested static profiles which disables DLM and then been able to adjust SNRM at user end, but I'm not 100% sure on this. Most people on ADSL service report they've switched back to PPPoA from MER recently. MER seems to be used by FTTC customers now.
MER isn't really anything special, its similar to the way BE and O2 handle ADSL and could be more efficient as it doesn't use the PPP overhead. In Sky's implementation your client device needs an adjusted DHCP that sends the userid/password as DHCP option 61. Most routers don't do this. Some Billion and Draytek kit has beta firmware that can.
2. I was getting just over 1 Mbps upload when I had Sky's ADSL service.
Some people report that DLM can get you 1.3 Mbps upload, but if you're on a static profile the max is 1 Mbps.
3. It is fully unbudled but it is a lot easier to switch between LLU providesr now.
I believe this is the case; Ofcom have improved things.
pro (16.8/1.2) - Ordered Sky Fibre Pro 45.6/6.5 - 4th sept
13 years of broadband - ntl:cablemodem/BTbusiness/metronet/bulldog/BE/Sky