I'm not familiar with the "data grid view", so I have no comments on 
whether there's anything precisely equivalent. There are a lot of of 
portable XML editors, including several which happily plug into or work 
smoothly with Eclipse (which is in some sense the portable equivalent of 
Visual Studio)... but I tend to either edit my XML entirely manually (eg 
with Emacs XML mode) or entirely programmatically, so I haven't had 
reason to go looking for compromises between those extremes.


Generating a schema from an XML file... "That trick rarely works". It's 
certainly possible to automatically generate ONE OF the possible schemas 
which describes a document, but that will generally be over-specific in 
some areas and under-specific in others. There are tools which will take 
a collection of XML files and attempt to derive a common schema that 
covers the whole set, but success still tends to be limited; at best you 
may get something that's close enough that it's worth using as a basis 
for manually taking it the rest of the way.

Designing the schema first, then using it to guide creation of instance 
documents, is the ideal approach. If you aren't ready to do that... 
maybe you should be sticking with well-formed documents until the design 
settles down?