All I can say is that you are not alone and really I could have written your post as my experience was pretty much identical although I also had extreme vertigo constantly before removal and at times after removal (and major blood Sugar swings). The anxiety and Depression were my worst symptoms also as I had never ever had these before and like you the Depression would hit that day or two when I would expect my period but it never came. Then after removal I would feel so flat from day 4 - 14 (just like you... amazing coincidence).
I had my mirena removed feb last year and over time have seen great improvement. Alot of it was just time (things did improve a lot) but really the greatest benefit (really I feel great.....and like my brain is functioning again at full strength) has been in the last couple of months when I have been on 0.5mg of bioidentical oestrogen. I cant believe the change in mood, outlook and memory....plus my blood Sugar is now balanced and I have no dizzy attacks. So good luck with the blood tests and make sure you see the actual numbers as sometimes mine was just inside the normal range sometimes just under......my gynaecologist said some women just need a bit more than others so was happy to prescribe it.
Please let us know how you go with your tests and how you are doing. Don't give up hope as I am sure with time you will get better. I know you are seeing a natuapath but I have also been working on balancing my diet with eating a fat with Sugar eg fruit with yogurt, vegi sticks with dip, and adding suppliments of magnesium, fish oil and vitamin B's.
You are right it is a hormone imbalance (which I believe leads to an imbalance in brain chemicals)! therefore with time, rest and nutrients your body will rebalance so please take care of yourself and remain hopeful.