Re: What should my target weight be?
First off: what exactly is your goal? You can determine your weight after you've set your goal. If your goal is simply fat loss, your weight should be set accordingly. If you want to lose fat ánd gain muscle, you shouldn't put your weight very low.
The BMI scale is not a good scale in my opinion. It doesn't hold anything in account. The numbers are determined by average numbers and every human is different.
You can use it as a guideline, but you shouldn't take it seriously. For example, a male, 6 ft - 180
pounds would have his BMI at almost 25. That would be a bit high. Say that person is very fit an muscular, at 8 percent bodyfat, he would be perfectly healthy but according to the scale he would be on the border to being overweight. Do you see the problem here? Also, you've got men/women that are in the perfect BMI range but have 35% bodyfat.
Going by fat percentage is a much better idea. Sure, you can monitor your weight, but keep in account that if you lose fat and build muscle, the scale might not change--it may even go up (since muscle weighs more than fat.) I'm actually on a fatloss regime myself, and I'm training with weights and doing intervals to lose the fat. I've lost 10% bodyfat so far, but the scale only shows a few
pounds of weight loss. My pants are much looser now and I see muscle definition. I think that in order to stay motivated, you should measure yourself to track your progress (including body fat stats) and use the scale "on the side."
You might even want to make pictures of yourself every week, so you can see the change. Sometimes, because we see ourselves everyday, it's hard to notice progress. And progress is what motivates people. So use different methods to track that progress.
As for 8,5 percent bodyfat, that's quite a stretch. Try setting your goals to reach 15% first (that's actually quite lean already. For women, it's the desirable bodyfat percentage.) If you're still not satisfied by then, you can think about going for the single digits. But make no mistake, bodyfat percentages beneath 10% means you're very, very lean. Only bodybuilders and fitness models get lower.
Hope this helped. I'd gladly help you out if you have any more questions.