Mendix 4.3.2 uses Dojo 1.6 (even dojo.version.toString()="4.3.2 (24595)" ?), the one in your link is version 1.8. So:
You cannot use dojo chart library of version 1.8 for Mendix. But you could include the dojo chart library version 1.6 in your widget. (http://dojotoolkit.org/documentation/tutorials/1.6/charting/demo/basic-declarative.html)
The code is belonged to Dojox and excluded by default from Mendix. So you have to add it manually.
Yes