Sounds about right for sky then. Pity it has capped you. What I liked about BE (when it was active) was that as soon as your line imrpoved you got your Max speed back.
Unfortunately DLM is a bit if a nuisance but I can see why it is there. Saves loads in unnecessary visits from BT or similar. With BT's DLM system they usually go back to normal speeds after a few days of problem free usage. Don't see why skys wouldn't. I didn't stay with them long enough to find out. My last two isps were bought over by them so jumped ship on activation days.
Did you do a lot of re-syncs over the past few days?
I did specifically ask if speeds will go back to normal after a few days if everything is stable but was told it's capped at 5MB/s and it wouldn't go higher, only lower.
I've had around 1 to 2 disconnections a day in the past few days perhaps a bit more the first day I've got the modem but last 2 days it's been pretty stable.