Creating a sub window

1)Yes you can use your own ID, however if your also using wxID's best make sure none of your ID's are the same as any wxID's that your using.
EDIT: make sure you change the id on both the create function for the object and the connect function.

2)You should just be able to put it in the .exe with Resource Hacker (wxWidgets might have it built in, not sure.)

3)not sure