it's hard to say. I would lose weight on 1500 calories (albeit slowly), but some people would gain. I've been in maintenance for several years (and have been hanging out on bariatric boards for about eight years). I know people who can maintain on 2000 calories, and others who can only eat 1200. You can always experiment with different calorie ranges and see at what point you lose, at what point you maintain, and at what point you start gaining. That's really the only way to do it other than the RMR test that someone above mentioned.
at any rate, 1500 calories isn't that much. Some people do gain on that, but then, you're pretty tall so I'm guessing you'd either maintain or lose on that much.
also, the closer you get to a normal BMI, the slower weight loss becomes. That's just a fact.
1200 calories is super low, unless you're short or have an incredibly low metabolism. Most people can't really sustain that forever. Personally, I'd give up the ghost on that one. As I said, even 1500 is pretty low for most people....sustainable, but low. I wouldn't worry about it unless you're gaining on that.
for the record, I can maintain on 1500-1700 calories. If I'm doing some heavy exercise, I can go up to 1800 or so - maybe even higher.