Nifty! Nice job on the sewing! My DIY 4mm Cherry Vibram have a several holes from trying a variety of straps and ropes, as well!
It seems that basic sandals either strap across the toes or in-between the 1st and 2nd toes. On my first version, I used the strap across the toes method, as my toes were too squished to tolerate the in-between method. After a couple of years, as my toes began to spread, I could no longer tolerate the strap across the toes. My bunions were improving, and the straps were too uncomfortable, no matter how I adjusted them.
Eventually, I got around to redoing them, and used the in-between method with rope. It took a while, but eventually I got used to them by learning how to spread my toes wider (which was even better for my bunions).
I don't think that you'll have to worry about someone stealing your design, because essentially all basic sandals are variations on the themes of either strapping across or in-between the toes. How each manufacturer does it, is a bit different.
Nice job and good luck!