I found a decent calendar app for the iPad that does what I was looking for, that I actually like! Calendars+ by Readdle.
It allows me to view not only multiple Google Calendars, but it also displays my Google Tasks on their due date. Productivity is returning to normal levels now!
While I still haven’t found a program that beats the old Windows Mobile app PocketBreeze, the Pure agenda widget I was using on Android was close. However, Calendars+ at least gives me back a usable agenda view using my data in my Google accounts on iOS, and that’s good enough for now.