How to know what goal weight should be?

I'm 5'4", 60 years old.  My surgeon said we'd call success 175 because that would be overweight instead of morbidly obese.  I set my own goal at 149 because that would be 100 pounds down.  WW says my Lifetime goal is 146.  I haven't been in the 140's since 1975 after my pregnancy with my son.  Heck, I hadn't been below 189 since the 1970's either until Sleevie came along.  I'm having a tough time staying at 159 with an hour of daily exercise and calories under 900 and low carbs. I was under 800 until a couple of months ago.  I know I need to dial the calories back to lose but honestly, it's tough at 13 months out.  I'm seeing my surgeon this week and will talk to him about where I should be weight wise and how to get there, but that said, he'll probably tell me to just keep doing what I'm doing.  I learn so much from everyone here and really appreciate it!  I'm not giving up on my original goal of 149.  I've always always always given up and gained the weight back before.  I'm visualizing my success this time!

 My surgeon never gave me an idea.  About the closest he came was telling me that because I didn't have DS it'd be good for me to see 60-70% ewl and he expected I would stall out around 200.  I am currently at a little more than 88.5%ewl and though today it feels like I will never lose another ounce, I sure do plan to.  My first goal was century club, my second is to be a normal bmi, 164 (was hoping to make by surgiversary, but that's 12lbs. by Memorial day, and the way things are going currently, I'm afraid I'll fall short), then 150, and my ultimate goal is to be half myself at 138.5.  I think that would be a good-looking number on me because the closer I get to my "goal" the more I see what needs work.  I'm 5'8 btw.

My surgeon set my goal for me, but it was a weight that I had been close to about 15 years ago. I thought it was a reasonable goal. Today when I saw him, he said my range could go 5 lbs lower, and I agree with that also. I am 11 lbs away from the original goal and can see that another 5 lbs is within reason. As I get closer, I'll see what happens. I'm still losing about a pound a week.,..barely.