InfoPath Dev

It really depends on several factors.  1) Whether is it a browser or full-client form 2) What type of authentication does the web service use?  Windows Authentication, Forms authentication, WS-Security ? For browser forms, you will need to use SSO (SharePoint2007) or the Secure Store Service in SharePoint 2010 to ...

Are you using the External Item Picker, or just a standard List data connection to the SharePoint list? And does the form work when actually deployed, and not in preview mode?

Based on your description, the workflow never finishes and is stuck waiting on that field to change to StageX.  Is the form by chance getting checked out?  That would prevent it from triggering until it was checked back in.  And if you wait on another field, can you get it to trigger?

It is possible through C#/VB code using the .NET Framework, or through a web service like Qdabra's Active Directory Web Service http://www.qdabra.com/en/products/ADWebService.aspx

I would think this is related to the zone the url resolves to in IE.  Check if the internal link resolves as Local Intranet or Trusted Sites.  If it is in the trusted zone, then add the external link to trusted sites and see if it still works. And where are you publishing the form?  Is it to SharePoint, or a network share?  ...

This is probably a limitation with InfoPath 2007.  You might try creating a calculated column so that it appears as a standard text column to InfoPath.

You may want to take evaluate the Excel to InfoPath tool here: http://www.qdabra.com/en/products/ExcelToInfoPath.aspx It can take an Excel workbook, and generate xml files based the template you provide.  For an InfoPath form you would just use the template.xml from the xsn.   A mapping definition you create will determine the how ...

InfoPath browser forms do not support custom task panes. You can find information regarding distributing your add-in for InfoPath filler forms here: http://msdn.microsoft.com/en-us/library/office/aa946869.aspx

I believe you just need to set the filter for the 'set a field' for the _Requestor line 

Is that the actual value inside the <udc:Query> element or did you decode it for clarity here? Can you attach the entire udc file ?