Probably your best "protection scheme" will be to move fast on the market once you're ready.
Show and sell as many copies of your work as you can in a short time frame. Make customers happy with you, your sw and your business model.
At that point, even if someone steals your code (or even the rough idea at its base) it will be quite difficult to knock on the same doors you already visited and where you were appreciated. Why leave the nice, dependable guy (you) to switch to the newcomer?
Trying to technically protect your sw is time and (mental) energy consuming. Use that same time (and energy) to expand your client base, add features and costantly refine your sw. Clones will arrive on the market, but if you keep the entry barrier high enough you'll end up in a comfortable, well protected state.