I don't think it matters how you cancel your score as long as you don't have a 120 there because you didn't. If you have the option of canceling without going in, why waste your time? Contact LSAC. They're pretty nice.
Okay, as far as prepping- first of all, I'm scoring at a 161 right now, but I want to get that up because of my circumstances. I think I know why you're improving one week in one and then dropping in the other. Like I just told someone else on here, it's like a sport, you have to practice different things to be good at the sport and although you may improve overall over time, if you practice one or two skills one week and neglect the others, on gameday you will probably be greatly improved in those skills you practice, but you may drop a bit or significantly in the skills you don't practice. So, prep for all of the different sections all week and take a weekly preptest. Make sure you practice everything the day before too. Also, I don't know anything about Kaplan and it seems like people don't have great success with them in general. I am using Princeton Review's online self-paced lessons and I like them. I don't know if you can dish out another 800 bucks, but you get self-paced lessons, preptests, and a lot of practice in books. If not, just do what I recommend and hopefully you'll improve. You have to think about where you're missing questions and what you don't get and then look in your bibles in the index for that topic or those topics.