i immediately thought swales all over as well. also rainwater channeling in places where swales would not be ideal. could probably do pond(s) easy with such clay soil it would seal well. channel the water there.
amaranth is supposed to tolerate heavy clay well, it's got deep taproot mass, very tall (8-12'), beautiful ,edible .i juice and stir-fry leaves as well as in salad.the grain i have popped and boiled.
it reseeds like crazy and the stalks add nice biomass for mulch/compost. i will send you a bunch with our next trade if you like.think it'd be nice for steep slopes.
consolidating all those little
compost piles into 1 large heap would get it breaking down faster, a cubic yard as bare minimum is the rule of thumb ive heard and stick to.
can you source more organic matter from the forest in leaf or pine litter?
how about blueberry and other berry bushes in the forested areas nearer the house.
i'd get bamboo going someplace too. many do well in poorly draining clay soils.handy stuff to have around, good for erosion as well,could be a contender for those slopes.