Jaffrani bhai - we left Karachi at 6.30 AM, and reached RYK around 5 PM (maybe 4.45). It took approximately an hour or so longer due to bad roads - most roads between Matiari and Ubauro were under construction, which meant we were travelling very slow and hence wasted a lot of time. Secondly, on the RYK to LHR leg of the journey, it was a Sunday so Okara onwards until Lahore there was bumper to bumper traffic, which again took a lot of time. We left RYK at 9 AM, after fuelling etc. and reached Lahore around 8 PM roughly.
I don't think stopping at Sukkur overnight would be a good idea. RYK might be better since it is roughly almost halfway between Karachi and Lahore. If you stop in Sukkur, the first leg of your journey will be very short, and the second leg much longer. So do think about it.
Yes, all documents must be complete, as I've heard from fellow PakWheelers re police harassment at Ubauro, while entering Sindh.