Thanks all for your replies. I did wrote to Profile Design to hear their thoughts, but haven't received an answer yet.
The sweat issue was brought because we did saw some corrosion on the stem, as you can seen on the pictures below, and the paint did peel off very easily. I do sweat a lot and I do use the trainer once every two weeks, for a 2 hour session, so it is exposed to a lot of sweat. However, I'm sure this should not have happened, the stem should handle sweat without issues, that's why this is so puzzling to me and think that maybe the stem was defective.
Regarding weight, yes, I am a bit heavy, as "therhodeo" pointed out (tri guy lol), I weight 185 pounds. The amount of stacks is because that's how the bike was setup during the bike fitting.
I guess as some of you say, this could have been the result of various factors, but just the thought of this happening downhill scares the #$&% out of me. Don't know if the mix of the stem being AL with a Carbon wrap caused this, so I guess I'll stay with an AL only stem.
I got a new Bontrager AL stem, and I guess from now on I will check the stem more regularly and change it once every year, since I wouldn't want this to happen again.
Here are the additional photos:
