How many calories a day?

Hey everyone,

In addition to doing a program I'm counting calories to know how much I'm actually eating a day(turns out I was overeating by a lot!), but I'm having trouble with goal setting.

I hope someone here can help me figure out how many calories to eat. I've calculated both my tdee(1734kcal) and BMR(1445) at my current weight. Tdee and BMR at my goal weight would be 1587 and 1323.

All the advise I've read said to have a 500kcal deficit, but that would put me at 1234kcal so under my BMR. It's even under my BMR at my goal weight which I've read is a no no. So should I just eat my BMR, so I'd have a ~300kcal deficit at least? Will that still have me lose weight? I have Hashimoto's thyroiditis, so I'm prone to putting on weight. Does this have any affect on tdee/BMR?

ETA: the last 10 days I've been eating 1300 +-500kcal a day and not felt hungry. I'm drinking 2-3L water a day.