Add-in sure is wrong 55 deg is BS Whitworth angle of thread where as Metric is 60 deg.
DID you look at the OTHER attachments the square cut thread example??
Here is the part that thread on that spindle mates with, it'll give you an idear of how to cut/form internal threads, then add a not on your drawings.
I did look at your examples, thank you for providing those. I now understand I should stay away from the add-in. I hope people are not blindly using it expecting the threads to turn out correct. It got me in a little hot water here at work!
From the Quick Start.doc
British Standard Whitworth
Post some screen shots.