deficit near goal/fat loss cycle cookie monster hormone?

Hi,

I've googled and searched the forums before I posted this, so sorry if it's been asked a million times; my search skills aren't the best.
How do you calculate what percentage of TDEE your deficit should be according to your weight/body fat% in relation to goal weight?
I'm near on/near goal weight now but I'm still trying to lose fat and I'm all over the place messing about with deficits.

Also I remember reading something about fat loss cycles and a hormonal change or something similar at a stage in the cycle where you will feel like you need to EEEEAT like a cookie monster, and you need to fight through that and you will lose? I can't remember where I read it, if the source was credible or find any more on it. Does that ring bells with anyone? I don't mean set point weight, I know your body will fight against going under set point weight, but this was supposed to be something that happened periodically throughout fat loss?