I think you're definitely putting way too much pressure on yourself. Above 175 is extremely difficult to obtain. I'm sure you can do it, but accepting nothing less than 175 might be an unrealistic goal. It is hybris to assume one can obtain a score of 175+ for certain. Anyways, I'm not sure what school you want to go to, but ~170 will get you into almost every tier 1 school, unless you are aiming for Harvard, Yale, and Stanford. So you really have nothing to worry about. Stressing to obtain 175+ might not be a good thing, b/c you'll be more inclined to cancel your score when you might've done very well on the exam.
Postponing until October is definitely a good idea. I made that choice too. You can always rationalize your decision that more time to study is always better. My reasoning was if I wrote it now, I am most likely to get circa 165, but if I study for a few more months, I can probably get my score to 170+. That is the difference between getting into Columbia or Georgetown (not that Georgetown is a bad school). If I'm gonna pay the same tuition, I rather be going to Columbia. As I learned the hard way, the brand name of a school does matter. Unfortunately, LSAT is everything when concerning law school admissions.
Hope this helped.