I guess the title kind of tells everyone what I want to know.
Just for background, I am on the wait list and super excited about going here for law school but I've been accepted to another 1 year (non-law) master's program and it's getting to the point where I have to start preparing for something in the fall and I don't want that work to go to waste if I happen to get off the wait list just before classes start.
Don't cancel your score. Schools will still see you wrote twice and you will learn nothing about your performance.
You can basically finish your applications this summer if you want to free up time to study in the fall. Let your references know you will be asking them now, and then send them the reference link as soon as OLSAS opens up for next cycle. Write your personal statement this month. You can tweak it/write additional sections for each school once OLSAS opens up.
Regarding the test: spend your time on LG to get your score to -0 or as close to that mark as possible. This is possible.
From my own experience, I was heading into a September write with a 159 under my belt, but that was with a ton of correct guesses in LG. I had been muddling through some large blue prep book on my own, and had no clue what I was doing. I met somebody who told me that I should withdraw from that session and write in December after perfecting LG. He also recommended that I try the LSAT trainer. I followed his advice and scored much higher than 159.