-Weather widget does not update No problem here on iPhone X
-Calendar "Up next" widget not updating Once again, no problem here.
-Notifications on lock screen do not group Same as above, have grouped with zero issues throughout betas.
-Battery section is a mess (IMO) Screen on and Screen off times make zero sense definitely a YMMV whether it makes sense
-Under Screen Time where the "Most Used" apps are listed, there are apps named '3016sd8fv1de65bv1' with a messed up icon. Makes no sense. What apps are those? went back through entire list, no apps appear that don't exist on my device
-Battery Life goes from 100% to about 93% within 30 minutes with the phone not even being used. Phone is just sitting on the desk at work. Battery Health states my Battery is at 100%. So the battery is not in poor health. Sounds like you have something running non stop in the background
IMO, you have a separate issue going on here for sure. To blame all of this on iOS 12 when there are few if any other similar complaints is a bit ridiculous. Have you done any troubleshooting at all on your end? I have multiple devices running iOS12, and have been for many betas, and have not experienced half the number of the issues you are describing here.