You can check out this page that the LMCC provides.
The gist of it is that it is virtually impossible to calculate how many you need to get right, but it is not graded on a curve.
"Prior to 2015, the pass score for the MCCQE Part I was 390 on the old 50 to 950 scale. The new pass score (427) translates to 440 on this old scale."
This means that you have to get a score of 427 combined with the MCQ and the CDM questions. But the test is evolving, meaning that it will give you harder questions if you do well, and easier ones if you don't. The harder questions are worth more points than the easier ones. So you may need to answer fewer, harder questions in order to meet the cut-off score. If you're really curious, read the whole page, as it goes into a lot of detail I don't want to reiterate.
Honestly, the long story short is, don't worry too much about hitting the bar, and just do your best! As for how to improve your score in a short time, I can't help you. If I knew, I would be doing it myself.