Hi Tc
I can understand your frustration - it's all so difficult to fathom out especially in your situation.
Thing is, some of your side effects eg large painful boobs, could be down to the progestogen in the Mirena, so i think you won't be able to tell until you get a (or two) blood test for oestrogen. That is the only way to knowwhether the side effects and flushes are due to low oestrogen or not. Are there instances of the implant failing? I can understand gel and patches sometimes not working due to lack of absorption but an implant is right there in the skin? I only put the point about tachyphylaxis as a remote possibility but just because it has been mentioned in the context of implants.
You don't need a test for P. Your SHBG and T tests will be illuminating too, since as Alicess says, levonorgestrel decreases the production of SHBG and also displaces T from it and therefore can increase free T in circulation - even without adding testosterone.
The Mirena gives out a much higher dose of progestogen earlier on so hopefully any side effects will settle with time. I think you have been on Femseven before and were OK with this? Apols if I've remembered wrongly.
I do really think you are in the best hands though through the Chelsea and Westminster who are amongst the highest regarded (English) menopause providers in the field I believe and Nick Panay is one of the top people. It just sounds like you have to keep trying different regimes but there will be one for you out there and they have years of experience I presume with women in your position, using tried and tested products, but are able to individualise and tweak regimes (off-licence) accordingly.
Hang in there

Hurdity x