Hello Ghost,
I recall Merrill Creek Reservoir has a good handicapped accessible fishing dock by that tower that goes out into the water. It's accessible by the side entrance, not the main entrance that that leads to the visitor's center. Although if someone in a wheelchair did fish off the dock by the boat launch, I couldn't imagine someone kicking them off it, but they might.
Here is a website listing New Jersey’s accessible fishing sites for people with disabilities:
http://www.nj.gov/dep/fgw/pdf/wcaccesslist.pdf