kraft seven seas dressing 180
Have you tried the (I think they are wish bone) spray dressings? They come in about 6" tall bottles, include all kinds of regular flavors, we have at our house: ranch, caesar, raspberry vinaigrette (because those are the ones we like). I think they only have a few calories per spray, and really do taste like "the real thing."
If you absolutely feel that "life isn't worth living"

without the full-fat dressing, try lowering the amount that you use. If I remember correctly, the serving amount is 2 TBS. That's a lot of dressing. if you use 1/2 TBS, that's 45 calories. You can either dip the tines of your fork in a 1/2 TBS dab of dressing, or you can take 1/2 TBS of dressing and water it down (or add a TBS of milk if it's a creamy one or a TBS of vinegar, etc). I'd suggest mixing your "new" dressing well, and coating the inside of a large mixing bowl, then tossing your salad in the mixing bowl.
Either way, you will find that your entire salad is flavored with the dressing, but you have 135 calories left over. I'd suggest using that for an afternoon snack, either a quick snack between classes or maybe right after school is out. It sounds like you have a too-long time between lunch and dinner.