The suggested solution to your Lens Buying Angst: keep the 50 but figure out why your wider-than-2.8 images aren't sharp enough!
There are several reasons you might be getting poor results at f/1.4 (some may be obvious):
(1) You don't have enough depth of field for your subject. Even a perfect lens, perfectly focused, wouldn't be able to get the shot.
(2) Your camera isn't autofocusing on what you want it to autofocus on
(3) Moderate overexposure-induced purple fringing (especially if used outdoors)
(4) Your camera/lens is systematically autofocusing too close
(5) Your camera/lens is systematically autofocusing too far
Problems (4) and (5) would require an adjustment to your camera that you may not want to deal with.
None of these problems are unique to the 50/1.4; you could just as easily encounter them on the FA77/1.8. Best to work this stuff out now before you acquire a taste for expensive lenses
.