At last, I got the case open! If anyone else looks here for that here is what I did. With all screws removed the case still is firmly attached to the front. I gently placed a long kitchen knife in the split between the bottom and the front and GENTLY pried them apart until I could see the latches inside. As each one became visible I used flat corn on the cob holders to push and hold each latch open as I went on to the next latch. About then is when I discovered why the case wouldn't budge before. There are little felt like strips glued along the joining edges between the front and bottom, and also between the front and top.
I don't see anything obviously wrong causing the volume to fluctuate, no loose connections. I'm wondering if it could be something relatively simple like the volume control pot itself. I found that when the volume is acting up, a headphone plugged into the front jack has the same problem. The volume is sometimes so quiet that you can't hear it, and at other times it's as loud as it can be and in both states the volume control has no effect on it. Tapping the case (Ma and Pa Kettle style) sometimes provides a temporary correction. Sometimes turning it off for a while fixes it temporarily.
Thanks for the info on the light. At least I can fix that.
