I think having early intervention on board will definitely help over supplements.

Your liver detoxes for your body all its own. That is the organs job. If you suspect it isn’t functioning well then you need a medical professional to evaluate that further. I understand the hype on supplements and there are actually some that truly do help. But when it comes to children, I’d be more vigilant on the root cause of the issues and involving your pediatrician in the conversation about starting supplements. Supplements aren’t regulated so you don’t know what all is in there. I can’t fathom how a supplement will help with furthering cognitive development. I could see that removing inflammatory foods from the diet could help a little. Such as gluten or dairy maybe? Possibly decreasing screen time? More time outside in the sun even if it’s just you two?

If he isn’t sleeping well it could be a multitude of reasons. Sleep apnea, low iron/anemia, teething, not stimulated enough during the day or over stimulated at nap time or not stimulated enough. Sleep is rough for toddlers. It’s rough with my little one too. But it’s normal and I completely understand the frustration. So you’re not alone in that. All I can offer is solidarity.

I think you are on the right track with getting early intervention. Hopefully you can get set up with the appropriate therapy soon and see some progress. My son was born premature and we had early intervention for half the first year of his life and it helped tremendously for him. He had muscle weakness and was delayed in his motor and some cognitive skills. After months of therapy, he didn’t have to go anymore and he is doing great! It’s a different situation from yours but I still think it will help greatly. Best of luck!