Great job, Stevin. Where did you find all that info?
I checked my handy US Divisions reference table [ My Ref Table ], and searched for a "50 Infantry Regiment" and "286 FA". As you can see, these don't appear in my table. That means that the 286FA was an independent unit that was assigned to Corps or Army----as you have state. I thou ght maybe Donna's source had identified the 50 Regiment as the 50 Division.
One phrase that catches my eye is she stated "50th Division Regular Army". That sounds like a term that was used prior to WW2. Of course, there wasn't a 50th Division even then but this might be a hint that her grandfather enlisted before WW2 and then was later re-assigned. I've discovered that any sketchy info of a soldier who changed units makes for a little confusion. But when more info is collected it all falls into place and matches up with enlistment dates and overseas service.
Steve