Yes, you need to turn off the Mac installed version of Apache so you can run MAMP. But, you found that out and so Im confused of what your issue is now? When you to go
http://localhost:8888 what comes up, anything?
Have you tried removing the "Include" at the bottom for the time being? Do you the Mac firewall turned off? If on, is 8888 allowed? Tried turning off your firewall to eliminate any possible issues.