Answers. To your questions.

Thank you for asking stuff in the post from two days ago, Suzanne and Marianne!

Regarding the Schnittbücher from the Kickstarter project, the Kickstarter books are scheduled to go out in June this year (though I wouldn't be at all surprised if it took considerably longer, knowing how things go in the publishing world). Marion says that they will be available  via Amazon US and DE after the rewards have gone out - so you will be able to get your copy.

And Suzanne asks about sewing techniques in 7th century. As far as I can tell, there are about the same stitches and techniques in use as for later sewing -with the exception of things like buttonholes, which were not yet so in vogue. There's a nice overview of sewing techniques published for the Haithabu finds (later than your intended period, though) and these are not too different from the later garments. There's not so much variation to be had for a straight seam, after all: running stitch seams and overcast seams are already found in the Hallstatt material from Bronze and Iron age.
7th century Frisians are, unfortunately, not very much in my core confidence zone either, and I can't think of any books with good textile finds from that era and region off the top of my head - sorry.