That sounds like what Image Ready does with the faded edge. With Terrazzo, you can select part of image (always best to work with image size larger than one repetition of pattern. You can adjust selection with Terrazzo) and see how it will looks as you move it around image and/or change size of selection.

300 dpi should have been good enough. You go much higher than that and you got one huge file. I've never scanned a fabric. I know there is a "Descreen Printed Originals" setting. I'm wondering if that might help. Not really printed originals but worth a shot.