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These articles will help: https://www.gardeningknowhow.com/edible/fruits/mango/growing-mango-trees.htm, https://www.gardeningknowhow.com/edible/fruits/pawpaw/growing-pawpaw-trees.htm

While mangoes are not considered a tree with a particularly invasive root system, it is recommended that they be planted 25-30' from houses, because they are quite large. If the tree at your building site is young, can you have it moved? If not, you can install a root barrier between the house and the tree. See more in this article: https://www.gardeningknowhow.com/ornamental/trees/tgen/problem-tree-roots.htm

According to my research, you can mix 4 tablespoons of wettable sulfur powder per gallon of water in a pump sprayer/spray bottle.

Source:
http://homeguides.sfgate.com/kill-powdery-mold-vegetable-plants-92349.html

I have heard of this effect, called Vivipary in tomatoes, but this is the first question I have seen with Mango fruit effected.

I did find that Mango also can suffer from Vivipary, which is generally when the fruit is overripe but not necessarily.
A natural hormone, abscisic acid or ABA is reduced and seed dormancy is lost.

It is an unusual occurrence in Mango and the seeds germinate while still attached to the tree.
The fruit look normal on the outside and only when cut reveal the issue.
The fruit cannot be marketed but are generally edible but may have taste problems.

The only information I found on management of this issue is to improve growing conditions and manage environmental problems.
You may want to contact your local County Extension Office to see if any other growers are having this growing issue.

https://www.gardeningknowhow.com/edible/fruits/mango/growing-mango-trees.htm

A Mango Tree can generally survive some heavy rain without issue if the soil is well draining.
If the roots are sitting in wet soil, this could certainly stress or kill the tree.

Also a Mango Tree should not be exposed to temperatures below 40 degrees F. If the tree was wet from rainfall and the temps were cold, this could be a deadly combination. A dry tree will have better chances in cold weather then a wet tree.

You will need to wait and see. You can prune away any dead material and hope the tree will recover.

https://www.gardeningknowhow.com/edible/fruits/mango/growing-mango-trees.htm

Here are some links that will help you with fertilizing information.
We would suggest you contact your government offices to receive information on export laws on commodities.

https://edis.ifas.ufl.edu/mg216
https://www.ctahr.hawaii.edu/fb/pineappl/pineappl.htm