I just installed that webpart and the main reason why it's not working is because 'LoadTransformation' is moved from CMSDataProperties into TransformationHelper in k11. I imported web part (followed instructions from blog that you shared here) and on line 212, you should change this:
br.ItemTemplate = CMSDataProperties.LoadTransformation(this, Transformation);
br.ItemTemplate = TransformationHelper.LoadTransformation(this, Transformation);
After that, rebuild solution, solve errors in console(in my case I had some problems with CustomResponseRepeater.ascx.designer.cs, but I solved in the way that I created new clean .ascx control and then just copied code from imported custom webpart).
You can also find proper package for kentico 11 in this post, called 'v11.0.10'.