135 at 16 pounds... you mean 135 C if it is 135 C then it should boil at about 275 F....

i wouldn't trust the gauge you put in, 260 doesn't sound right it should either be creating so much pressure that it boils over, or you are bleeding out pressure (and losing water...). a 195 should be wide open by 215 perhaps it has broke closed?? perhaps the radiator is defunct?? if you were in the states i would suggest finding a shop with an IR temp snesorand verify your results, but i dont know if you have acess to such toys.