I agree that you really should check with a doctor about your thyroid issues before doing anything major to your diet. I am not an thyroid expert. My only experience with thyroid issues was that I had severely compromised thyroid function as a result of chemotherapy that has been healed by eating on the PB plan.
Even if you don't change your macros a whole lot, I would recommend eating more but less often. See if you can get to just the 3 meals, then maybe 2 meals and a snack, then to just two meals. If you give your body more hours in between feedings, it has time to switch into fat burning mode. If you keep feeding it often, it says, "sweet, fire up the fat storage, lets put some of this away for winter".
High fat items I am finding useful in my keto plan : bone marrow, bone broth, coconut products, avocado& avo oil, fatty dairy such as butter, cream, cream cheese, mascarpone cheese, brie, liver pate (I make my own).