AV2/L1 is the SCART socket, so if you're not getting sound then it indeed sounds like a SCART lead problem. Try connecting Sky+ directly to the TV using the same SCART lead and see what happens.
Prog 6 is the internal analogue tuner, therefore if you get poor picture then it sounds like your reception isn't very good. Is the aerial plugged in directly to the DVR or is it daisy-chained from something else? If daisy-chained, try plugging the aerial into the DVR directly. Also make sure the channel is tuned in precisely.
If Prog 6 is the output of your Sky+ box rather than a normal channel, again make sure the DVR is tuned into it properly. Also try connecting the output of the Sky+ box directly into the TV using the same aerial lead in order to eliminate the lead from the equation. But if you've got the Sky+ box on SCART anyway, why do you need it fed in via RF too?