This answer is based on my knowledge of the function of other cameras (Canon, FujiFilm) and examination of the Lumix DMC-G7 manual. By understanding how other cameras work, you may be able to find the equivalent functions for your camera.

1. You can download the manual and firmware updates from the Lumix DMC-G7 support page. Perhaps updating the firmware will make the camera behave as you desire.

2. When some cameras go into manual-focus mode, they open the aperture wide and display the exposure with the greatest contrast (the "proper" exposure) because that is the easiest setting at which to focus manually. When you are done, they switch back to the previous display mode.

   • Although some cameras do not behave this way, the feature most likely cannot be turned off in those that do because it is an intentional design decision. Upon examination of the user manual (pages 165-170), it seems your only option would be to turn off MF assist.

   • If you desire a zoomed in bright view for focusing while also showing the full view with the exposure settings you've selected, you should make a feature request directly to Panasonic.

     Although I have never encountered a camera with the ability and there may be other technical reasons why it is not done, @mattdm states:

     theoretically, a camera could show multiple possible exposures simultaneously. The live view preview of exposure is faked anyway — live view uses the widest aperture and some constant, short "shutter speed", so it must be all done with amplification.

3. After manually focusing and composing your shot, you half-press the shutter button and the camera refocuses, which defeats the purpose of manual focus.

   • Some cameras have an AF+MF mode in which it auto focuses on half-press, but allows you to refine focus as long as you continue to hold the half-press. If you stop half-pressing, it will again AF. To avoid this, either press fully without releasing the half-press or use full MF (disable AF).

4. AF, MF, and AE are all acting independently of each other somehow.

   • Some cameras allow AF to be moved from the shutter button to a "back button", usually labeled AF-L (Auto-Focus Lock). This button, along with AE-L (Auto-Exposure Lock), can be used to replace the half-press to some extent. Check that AF-L and AE-L are set to your preferred behavior.