Thank you for your enquiry.
The Formativ applet .vbf file structure you describe is correct for Formativ 2.0 and above. While the .vbf file contains XML tags it may not be well-formed XML, but Formativ does not require that the XML be well-formed in order to run an applet.
Can you say what was the exact text of the “XML parser error”? Perhaps a screen shot would be helpful.
The Formativ IDE provides the means to edit script code and forms. For an introduction to form design see the Developers Guide, under Creating User Interfaces | Visual Forms Designer.
See also this featured topic on obtaining further documentation on form design.
I hope this helps.