I fixed it! Not happy about it, but it's fixed. So I could not get the iPhone to force-restart. It was stuck in a boot loop, and nothing I tried got it out. My final step was to plug it into my iMac (which also works for Windows with iTunes). Once plugged in, I did another force-restart (volume up/volume down then hold the power button for 20 seconds). This broke it out of the loop and brought up a restore screen on the iPhone (with a picture of a cable connecting to a laptop). It only worked this time because it was plugged into the computer. In the iMac, I opened up the finder and looked under "devices" on the left side of the window, just below the hard drives, and found iPhone. Click on iPhone and it walks you through the rest. You have 2 options - Update and Restore. Always try Update first. I tried Update, and got an error message "unknown error (1110)". So I started the process over and selected Restore next. This deletes everything on your phone to bring it back to its factory settings. Once that was completed successfully, I did a backup restore from a recent backup from 2 days ago. Your iPhone screen walks you through all the steps of restoring from a backup. So it's working again.
