How to protect myself without a condom

Hi, imagine after a year and a half i'm getting to the end this !

I made a runtime application and it seems to work ok.

Now how can I protect the source code as best as possible. I figure their
will always be a crack somewhere but I want to give them a little bit of a
hard time to get the code.

For one thing, how can i disable the shift key when the application starts ?

And what else should i do or you can recommend that i do to protect this
application ?

Is it possible to split a runtime application and lock the structur of the
backend ?

Basically I want to lock this thing down so someone else can use it but not
look inside.

How to protect myself ?

Thank you for the tips.
--
Eric