That quilt is on my bucket list. I think the theory for reducing but keeping all the same blocks is to calculate the percentage you want it to be and multiply that percentage by each number on the pattern.
example.... if the blocks measure 24 inches finished and you want to reduce it. Figure out what size you want the block. Easiest is to make both of them divided by either 8 or 3. If you make the blocks 16", then you would reduce the measurements by 1/3. 24 x .333 = 7.992 24-8 (you round up the 7.9) gives you a 16 inch block. Or you could just multiply 24 x .667 = 16.008" finished. If you do decide to reinvent all your pattern numbers, I would use those numbers to cut paper to the sizes you think they should be, less the 1/4" stitching on all the sides and tape it together to see if it will fit. This way you can make any corrections prior to starting the quilt. If you use colored paper, you will be able to see the pattern emerging.
After looking at the pattern again...you are going to have a heck of a time with some of the smaller lines. I would think about making it a 2x2 block square and adding extra borders if needed to get you to the size you wanted. This is one where it was made 2x3 blocks, probably to fit a twin/full
https://search.yahoo.com/search;_ylt...yfp-t-252&fp=1