I'll try to answer your questions:
1. Could you please send us some pictures and code snippets or a sample project so that we could examine this issue and provide you the proper fix.
2. You could indeed use a converter (note: the MinimizedColumnWidth is of type GridLength now) or you could use the LostMouseCapture event like this:
sender, MouseEventArgs e)
.column.Width.Value + 3);
3. There's a feature request like this in our PITS
and you can track it here
We'll consider this feature for our next major release but I can't promise you anything because this can be easily done with a GridSplitter.
I hope I was able to help you and we're looking forward to hearing from you.