eating back calories

You don't need to but many people do, aim for half if you feel uncomfortable about eating them all but find your calories too restrictive

Your diary is not open so I can't work with your specific data, but i'm going to tell you a story.

If you have 300 miles to drive (representing a weight loss goal)
and you need 10 gallons of gas in your car to do it (your calorie target)
and then you siphon off 3 of the gallons of gas (exercise)
you're going to have a hard, if not impossible, time getting there.
Sure you'll go just fine for a while but eventually you will run out of fuel and your car (weight loss) will slow and stall.

hope that's clear enough

On an ordinary day, I walk between 1.5 and 3 miles. On days I walk to and from work, it's 7-9 and I get a lot of grief from my coworkers who don't like to walk. On days I hike with my husband, it's 5-10 hard miles with 15 pounds minimum in my back pack - that can be a 1500 calorie burn. Zumba days I burn somewhere around 500 calories at Zumba and 120 at a conditioning class before Zumba.

Ordinary days, I eat back none to half of my exercise calories. Walk to work days and Zumba days, I am hungry and eat back half to two-thirds. Hiking days, I eat whatever the heck I want and that usually still doesn't get me to half of my exercise calories. So I guess my answer to your question is I listen to my body and eat when it tells me to. And usually what it tells me too. Today is going to be a fruit day, I can tell already. Makes sense because I feel a cold coming on and my body needs the antioxidants to help fight it off.

ETA: I am also 45 and a mom of four with a desk job. And wish you the best on your weight loss. You have to find what works for you and then don't worry about what confilcts with that.

1 burn 400-500 calls a day at the gym.. i need to loose weight.. should i eat these back????

Depends on how you're planning your weight loss. At the most basic level loss is about burning more energy than you consume, so the work you do in the gym helps lead to that energy (calorie) deficit.

Not eating your expenditure back may lead you to lower weight loss, but subject to your net intake over the course of a day may lead to other side effects. While it's as simple as energy out exceeding energy in the balance (or loss) comes from all body tissues, not just fat. If your net consumption is too low then your body will be cannibalising muscle or organs as well as fat.

For the majority of women the lower limit for net intake is around 1200 calories, so aim to eat back enough that you're netting at least that.

All that said personally I only account for defined training; running, rowing, cycling. I don't account for the walk to and from work (200 cals per day) or heading up and down several flights of stairs each day at work. That means I have to be a bit more religious about eating back my training expenditure as there is a reasonable amount of unaccounted for expenditure already.