Well, the intercooler is after the turboin cycle, so it would be hard for water to get to the turbo, unless it leaked down from it o something, but thats doubtfull.
Cream coffee color, you got me. I have no idea what would cause that, unless the 5w-30 Mobil oil is just completely not acceptable for this type of application. I just use regular weight oil in my car, 10w-30 synthetic, and it works fine. The different oils do have different qualities to them, such as different particle break up temperatures. Maybe that oil was not sufficient for the turbo and caused it to ruin the seals, I don't know.
Water cooler, not coolant? I'm not so sure about this, since coolant is specially made to aid in cooling, as regular water just doesn't do the job. Otherwise, wouldn't we just use water instead of mixing it with coolant. This could be another possibility of why your turbo faulted, improper cooling.