What I’d suggest you do is to install the canon software that came with the camera. I’m a firm believer that if you need to edit more than lightroom/canon dpp can do you are trying too hard. You strike me as someone who is a visual/hands on learner and all the tutorials in the world won’t do as much for you as experimenting. Get the USB cable out and hook up your camera to the computer and get something to use as a model and practice on it. If you go for the right settings in the software and your photos will pop up on your screen a second after you took them. Adjust the settings as you go and play with the different settings. I would say start in AV mode to start with and then M mode when you start adding the flash into the equation. Play with the flash and see how the aperture, shutter speed and iso affect it. Even though you aren’t adjusting the shutter speed yourself keep an eye on it anyway and see how the aperture, iso and shutter speed relate. When you’ve completely understood the exposure triangle and how iso, aperture and shutter speed interact then start worrying about metering. Until then just go for the standard setting whatever it happens to be called. Something that will be more use than worrying about metering modes would be to understand exposure locking.
The newer rebels have decent enough AF, I believe it is the same as the older xxD models which means all the points are usable. Make sure you learn how to change af point without taking the camera off your face. The bigger bodies have a big ergonomics advantage there. If you are going to be working as a photographer you may want to consider buying another body anyway to complement at some point, a 5D mark I would make your 50mm sing and offer you better image quality than your current body can do despite the lower resolution and better ergonomics but a far inferior lcd screen.