I owe you $0.01!!! We checked "full image" (even though that was the default) and sure enough, the banner and cards are now scaling correctly on the android device. Thanks so much for the tip. Saved us a ton of work and we can stay in-budget on this project.
A few additional thoughts for those running into similar issues:
1. davidhicks_dps has some really good suggestions listed above to fine-tune the cards so that they have a better appearance on Android. If simply choosing the "full image" option doesn't do it for you, you can fine turn further using his % tip
2. We also changed our card design so that the title is at the top of the card instead of the bottom (full image with title on top of photo). This better accommodates devices where the "fold" may be different than you planned for so that a user can at least see what the card is without too much scrolling. There is more scrolling on the android devices due to the 16:9 ratio so the benefit is more obvious there
One issue crossed off the list.....moving on with our final testing!