a. There is a Non Commercial Version of Dangerous Waters Available. This Version contains some special feature e.g. DIS Protocol Support or a Build In database Editor.
b. hmm.. there must be something around. Someone wrote the plugin and there are some tools to open the J3D format.
c. No, but if you require Height Maps, check out
https://gdex.cr.usgs.gov/gdex/, you can find better and more detailed maps there (If you require DEM, then use MICRODEM to convert them)