What's your question? Ask

This article should give you some answers: https://www.gardeningknowhow.com/ornamental/trees/tgen/repairing-tree-bark-damage.htm

Here's some information that will help you: https://www.gardeningknowhow.com/lawn-care/lgen/eliminate-mushrooms-in-your-lawn.htm

It is certainly a fungus, but which one and how salvageable the tree is will be difficult to determine online.

With tree diseases, it can be very difficult to assess the health of the tree without seeing the tree in person. I would recommend that you contact your local extension service and ask if they can either have someone come and examine the tree or recommend a good aborist in the area to look at the tree. You can find your closest extension office (there is certainly one in your county) with this tool: https://www.gardeningknowhow.com/extension-search/

Sounds like it might be powdery mildew, https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm
To be sure, you need to have a knowledgeable person examine some samples. This link will help you locate one: http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/

Grafting is one of the most fascinating areas of plant propagation. The type of graft you use depends on what you're trying to achieve. An afternoon of googling "grafting" will give you volumes of information, but you might like to start here: https://www.gardeningknowhow.com/ornamental/trees/tgen/grafting-trees-what-is-tree-grafting.htm
Here's some interesting material on maple grafting: http://depts.washington.edu/propplnt/Chapters/Layering%20and%20grafting.pdf