You are indeed well-read, and I’m finding it difficult to give you an entire list, based on your tastes (which are remarkably close to mine). The two authors that come to mind, whom I haven’t seen on your list are
Greg Bear. Anything from him, but I particularly like the The Forge of God and Anvil of Stars duology. You complained about sad books, and these may be depressing, but it’s some of the best writing that’s still missing from your list.
China Mielville. Wonderfully weird and inventive books, in particular The City & The City and Perdido Street Station.
And since you mentioned Timothy Zahn, in comparison with Card, I take it you already read his The Icarus Hunt? If not, it’s also highly recommended for its unabashed fun and good plot.