I wud suggest to keep urself confined to OG and other official material only. If you have done OG throughly then get the paper based tests(from ETS) and practice them. Thats the best thing you can do to urself.
The material by others(non ETS) may seriously hamper the line of thought u have developed to solve the ETS problems by doing OG.
However, are u planning to apply for second deadline(jan first week)?. i am retaking my GMAT(after 650 in first attempt) and am really worried if i wud be able to make it in second round.