Hi rjcontroller,
Thanks for clarifying what's happening.
It's possible that the individuals calling you are calling your Apple ID address with FaceTime Audio or FaceTime Video and it's ringing specifically on your iPad.
With the way you've described calls as mostly coming through but some ringing only on iPad, it occurs to me that it's possible the callers are accidentally calling the wrong destination from Contacts.
Try checking to see how they've called you in your call log history if possible.
On your iPhone, you can also go to Settings > FaceTime. Make sure your emails are checked off as places you can be reached by FaceTime at.
Do the same in Settings > Messages > Send & Receive.
On your Mac, check the corresponding boxes in the FaceTime app in FaceTime > Preferences.
Thanks for using the Apple Support Communities.