Maybe wait and see on further amendments. In my experience the soil is usually pretty nice after sitting for awhile. The entire east side of my yard is lasagna. I like the stones!
Regarding planting in the fall, I am in zone 4a/Minnesota and just planted some things last weekend. Still have a couple more to put in. I have planted into early October with success. Just mulch the new stuff well. But maybe it works here because of snow cover...
