I just found your thread and I love the setup. Nice plumbing. I really like having a sump in another room. It makes the tank so quiet.
I have a couple of questions. I honestly only skimmed the 33 pages but after I realized you were having fish problems the last few pages I went back to try to see the dates you set up the tank and when the fish went into the tank. Am I correct that you put the live rock in somewhere around Sept 20th? And started putting fish about 3 weeks later? You stated after getting the two triggers that you were tempted to get more fish but decided to wait, but then just a couple of days later you got the clown tang and wrasses. I know I have set up tanks quickly and they have been ok, but looking back on my tanks the ones I really made myself practice patience (that is hard) those tanks have always been better, even a year or two down the road.
So all that to say, is it possible that the problem wasn't the silicone as much as the tank might not have been ready for that many fish that quick?
Hopefully, you can read into my post I am not trying to throw stones or say you did anything wrong, just wanting to put another idea out there for discussion.
With everything that I read you did an awesome job building the tank and I am sure with time your tank is going to be incredible, exactly how you wanted it.
Bart