Hi Gina!
menopause!
It's upsetting when we have a routine that works for us, then suddenly it doesn't work. So your frustation is totally understandable. Vent away!
Stupid hormones! I'm lucky in a way because I went through menopause as I was losing the weight (the huge fat loss dumped a ton of estrogen in my system and bam, I was done). So I've always had to adapt to being menopausal in maintenance. Along with being hypothyroid, I'm sure it's why my calories need to be fairly low to keep the weight off.
I've read that when our ovaries start shutting down estrogen production, then our bodies turn to abdominal fat as a secondary source of estrogen. Hence the lovely menopot or menopausal donut.
I think you're on the right track with increasing exercise intensity and/or duration. Your calories are about as low as you should go, so the only place to turn is exercise. Exercise makes a huge difference at our age, both in how we look and in our ability to keep the weight off. Once we're over 45 - 50ish, it becomes painfully obvious who works out and who doesn't.
If you don't do some high intensity intervals when you do cardio, try throwing some in.
And I strongly suggest increasing your weight training. Part of the reason that our metabolisms slow down as we age is the loss of muscle mass, so we need to counteract it by sustaining the muscle we have. At our age, we have to work hard just to stay in one place. Adding muscle is terrific, but our first goal needs to be just keeping what we have. And that comes from lifting weights and really stressing our muscles.
I know it's really hard to get away from all or nothing thinking. You're right, this maintenance stuff is all head stuff.
But the only certainty in life is change and we have to adapt. It's hard to let go of what's always worked but try tweaking your program a bit and see what happens.
Keep us up to date!