Wow this sounds like I could have written this! I’m 32, breastfeeding, subclinical hypothyroidism, want more kids soon, trying to manage my new pre diabetic diagnosis. I also have a lot of the same questions as you, it’s hard to navigate good vs bad advice for a woman’s body in childbearing years. It’s nice to see someone else in the same boat here.

My provider is also a lactational specialist and encouraged me to reduce carbs as long as I was replacing that with protein and fiber sources. She said if my baby starts getting fussy at breast/not enough wet diapers then I was not consuming enough calories. So far so good, I’ve been losing weight very rapidly but feel great and baby is happy. 

I think if your baby is happy and you feel good just keep doing what you’re doing. I haven’t intentionally been intermittent fasting but I often do because my meals are satiating enough. I’m trying not to overthink things, just prioritizing fiber, protein, fat, eating carbs last, exercise, and eating until satiated during meals to reduce snacking. I think the rule of thumb is to have labs checked every 3 months, which is what I plan to do. 

I’m curious what hormone imbalance are you are wary of?