Your maple tree has a fungal leaf spot disease known as phylosticta.  It is not usually an issue except in years with massive amounts of rain, like this year.  It will not have much impact on the tree.  It may lose some leaves, but not damaging amounts.  Trees produce more leaves than they need so they can afford to lose a few. 

The dead branches have no connection with the leaf spot.  Something else may be going on with your maple, if you are seeing extensive dieback.  You may want to contact a certified arborist, certified by the International Society of Arboricultre (ISA).  They are usually associated with tree service companies, but often will make an assessment free, charging only for any work done. Find an arborist by following the prompts on the ISA website:  www.treesaregood.org

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