Thanks, guys!
My target school is HBS, so I have undoubtedly to reach 750 level. A few months ago it looked like a crazy idea of a mad man but now I have a hope.
In quant section I had 2 silly mistakes at my fist attempt and 4 (3 silly + 1 lack of understanding) at second one. I even got a wrong answer for the problem that I had seen before and for which I had written a long and detailed solution

Two preparation tests are not good statistics. But I have some thoughts what really helped me:
1. Do not spend more than 3 min per question. Likelihood to get a right choice is illusory but likelihood to harm other questions is very high.
2. I tried the RC technique that asks not to read whole passage. Unfortunately, it did not work for me so far. I found that my RC score can dramatically changes from 10% to 100% depending on my understanding of the logic of the passage. Maybe after my exam I will write a debrief with some interesting findings....
3. LSAT CR - the most helpful thing that I tried last time! I guess LSAT CR questions are the most concentration-sensitive problems, especially, when I added moderate noise. Moreover, they really helped me in RC, as the main point of my RC-approach is logic. And, of course, after LSAT CR I feel much better in GMAT CR. So, After I finish OG10th I will continue with LSAT RC.
4. I also used my experience as a rider of a sportbike. When I race at speed up to 260 km/h, the cool mind, management of attention, speed of thoughts, and restraint of panic are crucial things to be successful.