Wow, you're in a difficult position.
1. What kind of timer are you using?
2. What score are you aiming for?
3. When are you applying to law school?
I think you are only able to take the LSAT 3 times in a given two year period, but there was another post with a link saying that you could take it again if a school allowed you to. But still, you have to ask yourself whether you won't freak out even more on the third LSAT because so much will be riding on it. I don't think you are the only one who missed on games, either.
I took last June and yes, it was nasty. Also, it was in the afternoon and the test center was all hot, but maybe for you it will be different.
About time management, perhaps you should try setting the timer for thirty minutes instead of thirty-five, that way you will leave yourself the five minutes you might need in the real test.
Also, I find that the silent timer helps because you can budget time for each individual question. This calms me because I know just by a glance how I'm doing for time.
On cancelling, my biggest mistake last year was not cancelling the June score
So it's all up to you. If you trust yourself to do better and you know you can improve, go ahead. Oh, I also saw someone on lawschoolnumbers who had cancelled twice and gotten, I think a 170. Look at the people with 170 and try to find him and ask him this question.