GMAT Strategy

Please help me with the following questions :

Who publishes the SC 1000 and what do you think about it ?
I studied the Powerscore SC Bible and did all the SC material in OG twice, and learning a lot from this forum.
I seem to learn more SC by repetition and noticed some progress.

I studied powerscore CR book and did all CR material in the OG. I plan to go over all CR section in OG again and take few free LSAT exams online. What is more worth studying in CR ?

I feel that the Data Suffeceincy quetions in OG are quite more difficult than Problem solving!! Am I correct or it is me ?