How do I change FAMILY ORGANIZER?

To change the organizer you would need to stop family sharing and then restart it as you as the initiator. Sadly Apple doesn't allow two organizers. If you don't want to stop family sharing then you'd need to update the payment info in your wife's account.

Settings > iCloud > Family > select yourself > Leave Family Sharing. Everyone that is sharing would need to leave manually. Your wife could remove everyone. You can restart family sharing in the same place.

when I did this, there was a notification stating all purchases in the last 90 days will be lost. Is there anyway to change the organizer in family sharing without losing your apps, tunes, videos, books, photos, etc

This support document describes how to leave a Family Sharing group. Leave Family Sharing - Apple Support