What is "a reduction factor from the rule of thumb" supposed to mean?!?
Visibility and ceiling are NOT necessarily related, so there is NO NEED for any J factors of any description! If you have a 3000' ceiling but heavy rain, visibility may be less than 500m, and NO "reduction factor" will change it. Either you see the runway environment at the decision height, or you do not. You either land or go around, respectively. Why do you want to make it complicated?!?
If there is a 200' ceiling, you will either see the runway environment at the decision height, or you will not, depending on the exact height and density of the cloud at that point. You will either land or go around, respectively. What else is there to understand?!?
It makes NO DIFFERENCE if you are "in the Asian part of the world where tropical thunderstorm and rain prevalent" or in another part of the world where snow or fog or rain occasionally pass through.
Uplift of fuel depends on MANY factors, including "an assessment of weather for contingency planning." If you think the weather will be near minimums, uplift more fuel if you think you may have to hold or want to make more than 1 approach before diverting.