To stop apache you can give a command on terminal:
# httpd -k stop

To start apache again, give command:
# httpd -k start

Please feel free to develop a more ergonomic and elegant way do to this. To learn more about apache command line options give:
# httpd -h

gstmjpg consumes quite heavily cpu, but apache doesn't (if you don't have many visitors on your tablet web). You will see this by giving a command:
# top

That shows how different processes consume cpu and memory.

If you have difficulties with port forwarding to enable access outside your private network (from Internet) to your tablet, you will find good instructions from this site. They provide detailed walkthroughs on how to setup port forwarding in diffrent routers.

As a bonus you will see your external IP address from their site. If you visit their site with your tablet browser, you will see the tablets public IP address (that is the address you have to go from Internet to acces your tablet)

-kepler