I see all of these weeds here where I live except the black nightshade and carpetweed. Ground ivy is so invasive here, it's just about impossible to get rid of.
Mullein flowers can be used to make an effective treatment for earache, and I believe the leaves have a use for lung problems, but I don't remember how they're used.
I think that lambs quarters is a type of amaranth, and as you said, it's leaves can be used like spinach. I suppose you could collect the seeds like other amaranth, but I think cultivated amaranth has larger seeds.
I've never even seen lamb's quarter seeds. They must be small. And I didn't know mullein had uses! Glad somebody recognized these plants.