By my calculations, your ideal weight would be around 130 to 135 lbs, right? So you're about 35-40 lbs overweight. At 5'6" and 268 lbs (over age 40 and with a BMI over 40 as well), I wonder why you're going the surgery route. If I only had 35-40 lbs to lose, I'd be ecstatic. In fact, 170 looks really good on me and I'll be lucky just to see it again. Do you have any health problems as a result of the weight, such as diabetes or high blood pressure? Both of these health problems would be good reasons to consider a sleeve. Have you seen a nutritionist or had your thyroid checked? If I were you (and could do the last 100 lbs over), I'd be seeing a nutritionist (seriously can't believe I didn't do this sooner), getting your thyroid checked, getting checked for PCOS (if you have any other symptoms), and getting more exercise (which is hard for me to do at the moment).
I think you'll be fine, since people can still eat/eat the wrong things with their sleeve. Further, the sleeve will stretch with time, making weight gain inevitable if you don't change habits. I tend to think of WLS as a last resort, and it isn't clear to me that you have run out of options.