It's not moisture that causes the melting issues in the tails - it's the high-resistance bulb connection and poor conductivity of the steel assembly. The high-resistance connection gets hot and melts the plastic, decreasing the connection tension, which causes the connection to get worse...
The LED flickering is caused by two things - the cold monitoring of the lamps and on the later LCI cars, the PWM power being used to run the lamps.
The dash warnings are due to the reduced lamp load, causing the LKM to determine the lamp is blown/missing.
And yes, all of these issues can be addressed, if you really want to throw more stuff at it.
