Why not go back to putting the 190 thermostat in as you originally said you were doing.
The installation just was'nt done right so it leaked! Do it right with a hole drilled in the top of the thermostat and get yourself an automatic fan switch that switches on at about 190 as well.
The switch needs to be mounted in the bottom of ,or the cold side of the radiator, so that the fans only kick on when that cold side gets to 190.
Make sure that all the air is out of the system.
