I think you may be overthinking this block. It is a 9 patch block. The center blocks on the outside perimeter consists of a HST and a QST. The outside corners and center are simple squares.

Make each part as a separate unit making sure they match the size you need. I do not believe you have a 5.75 finished block there. It's not a size that is normally made. I think it should be a 6 inch finished, 6.5 unfinished block. This makes all your parts of the 9 patch, have to be 2.5" before they are sewn together. Cut your corner and center blocks, then overcut your 4 center side blocks and piece them as the QST first, then add the HST to them, then square them to 2.5 inches. Then put it together in rows. Can you give us a link to your pattern? and/or the name?

Measure your rows. Each of the 3 rows should be 2.5 inches by 6.5 inches before sewing together.