What's the TSH level to maintain for 57+ female with Hypothyroidism, whose one & half of thyroid glands were removed for goiter surgery 15+ yr back?

Don't base on TSH. I believe it is a mistake to base dosage on TSH alone; TSH is a surprisingly poor marker for tissue thyroid levels in many common conditions; one should assess Free T3 (liothyronine) and Free T4 and also take how the patient is feeling into account. Here are good articles about how 11 renowned specialists optimize thyroid hormone levels: http://tinyurl.com/6gvsxqu Also see http://tinyurl.com/nrww2qg.
Normal. A lot of it has to do with how the person feels. but assuming she feels well, there is no persistent goiter and there was no cancer, at that age you would be aiming for the mid normal range of approximately 2 mIU/L (nL: 0.4 to 4). You would want to avoid under treatment and symptoms, but also over treatment and possibly cause palpitations or accelerate development of osteoporosis.