Your tree looks like it is in serious decline and is dying.
Your first photo shows a lichen, which are harmless and an indicator of good air quality. They are interesting organisms. Here is a page about them: http://extension.umd.edu/learn/did-you-hear-story-fungus-meeting-algae-and-they-took-%E2%80%9Clichen...
We can't tell specifics from your photos, but there could be multiple issues involved, but we would guess it is environmental, not due to disease or insect pests.
It could have been planted too deeply, or mulched too deeply, which can kill trees slowly over time. Maples are also prone to girdling roots which encircle the trunk and eventually cut off circulation of nutrients.
Take a look at our page that helps homeowners decide when to remove a tree here:
If you decide to remove and replace, you should know that Norway and Crimson King maples are considered invasive in our area and should not be planted. Red Maples are a possible native replacement.