Fonts disappearing is not a big issue that will ultimately render your page useless. If the font is gone, the look of the page is slightly affected, but the content of the page remains. It's honestly not a big deal at all.
Steam allows you to sell your game and provide players with steam keys from your own website without taking any cut. So that 30% cut that steam takes gets diluted quite a bit.
Epic does not allow for that level of distribution. It also doesn’t seem like they will.
Your argument about walled gardens also falls apart as soon as you realize that Epic is pushing for exclusivity.
Amazon’s strength is their logistics network. Any co-op you’ve just described will have an incredibly difficult time competing on shipping prices and speed of delivery.