Thanks for the info!
Will the Sky router allow me to force ADSL2 instead of 2+?
You cannot force ADSL2 BUT DLM can set the line to ADSL2
If ADSL2 yields less errors and better sync DLM should by default set it after 10 days
DLM goes for stability rather than speed. Their aim is to set a speed that means your line almost never drops sync.
As for using your own router being against T&C that's true.
That said when I was having issues on my line sky asked me to use my own router to rule that out.
Many people have used their own for years now with no issues.