You know, I do suspect a poorly-functioning liver to be a possibility. Even though the common blood tests come come out normal, every time

Its a common misconception that the lab tests for liver show liver function.  These tests look for cell damage including for some other cell types.  They do not show liver function.

I try TMG for a consecutive number of days I lose my sense of taste... which leads me to believe either my liver is greatly toxified or I have some kind of sensitivity to the TMG.

Not sure on why that it would cause that.  One of the most common causes of loss of taste is zinc deficiency.  TMG should not affect zinc levels directly, but it would not hurt to try supplementing with some zinc.

I did also have my amalgam fillings replaced with composites about 4 years back. I've read about certain materials affecting hormones.

I have been addressing that recently.  A lot of the claims being made are wrong or hype. For example, the claim that mercury is estrogenic has been going around.  But research shows mercury is an anti-estrogen.  But research on mercury has also shown that the effects on the hormones are minimal.  In fact, the whole issue over mercury amalgams has been way overblown.  Studies have shown that most of the mercury comes out of the amalgams within the first two years of being put in.  Then there is the issue of half life, which for mercury in the body is only about 2 months.  But mercury is also one of the least reactive of the metals, which means it can be easily displaced by a number of other common things like potassium , sodium, calcium.......  Considering how common these things are to the diet mercury would not stay even a few months in most people.  In addition, many of the compounds in our diet have a high affinity for mercury and other heavy metals binding them and removing them from the body.  Phytates from grains, algins from seaweeds and pectins from fruits and vegetables are all great examples.  This can explain why despite the humongous number of people who have had mercury amalgams, such as myself, that "Mad Hatter's" disease is not rampant.  I think people do more harm to themselves stressing over their amalgams due to all the internet hype out there than the amalgams themselves could ever cause.

I'll give those suggestions a try.