Cassava flour absorbs more moisture than all-purpose flour, so it will turn out dense if you substitute it 1:1. You could probably use just cassava flour, but you’d likely need to reduce it some (maybe about 25%) and keep in mind that the texture of the bread will still be different. I’d personally recommend using a gluten free flour that substitutes 1:1 for all-purpose flour like Bob’s Red Mill 1:1 Baking Flour.

You may be able to use flax eggs or applesauce, but I haven’t personally tried it.

love the blueberry lemon loaf

Yes, that would be fine!

That would be fine! It will be quite a bit of batter, so just be careful not to over mix after you add the dry ingredients.