Glad to hear things are working better! If you are using the first image, 600 is still going to be too big. The number you should enter is for how many pixels there are in 2.54 cm. (2.54 cm = 1 inch) If your book is a5 size, for example, your image would need to be 3500x4958 pixels to be 600 DPI. Just glancing at the shrunk images in the thread with the dimensions you provided, I'd bet you would get better results from about 250 DPI.
If you end up doing a lot of this, I would suggest photoghraphing a ruler. That way you can know for sure how many pixels are in that 2.54 cm space!
Sorry about the non metric measurements. Blame the folks at Xerox Parc in the 1970s and later at Adobe and Apple who defined the postscript standards we use for desktop publishing! It's not just you, it's everyone in the world except the United States that would prefer metric. (Although most folks from English-speaking countries still use both systems) It is the way it is since a US company made the first laser printer and defined the terms that are used.