Yup, maintenance calories for a "reduced obese" person don't follow the rules. Our active metabolisms (the calories we burn through activity, exercise, and everyday living) are about 20% lower than a person of the same height, weight, age, and gender who was never overweight due to our different biochemical/hormonal status. There's a lot of discussion about the science of weight loss and metabolism in Gina Kolata's
Rethinking Thin and we had a book discussion about it in the Maintenance Library if anyone's interested.
In a nutshell, it means that the person next to us on the treadmill is burning more calories than we are, even if we're putting in exactly the same effort. It stinks, but what can we do?
The average maintenance calories for members of the National Weight Control Registry are about 1400, with an hour of daily exercise. That's an average and of course, there's a lot of individual variation. And we sure see that here in the Maintainers forum! I think there's probably a 1000 calorie range that our members are maintaining in.

No wonder there aren't any "rules" about maintenance!
For me personally, I maintain on about 1400 calories and 90 minutes of daily exercise, divided between cardio and weightlifting. Like you, I most definitely gain if I increase my calories or decrease my exercise, as I've learned the hard way over the past seven years. But I'm 54, post-menopausal, and hypothyroid, so I probably tend toward the lower end of the maintenance calorie range.
ETA: just read Robin's post -- this is the sticky she's talking about
:
Some Answers About Genes, Environment, Obesity and Maintenance