Another thing or two I notice is .....
Sand your edges smooth and flat before marking the stitches (This will straighten those lines up).
This is more of an educated guess, but maybe your thread is too large in relation to you stitches per inch. My own stuff had that crammed look until I got the right mix of awl, thread, spi, and needle size.
The color and thread contrast look great.
Hope this helps and keep having fun.