Have you contacted your county extension agent? If not I suggest you do so. They will be able to suggest what sorts of soil amendment you'll need and what sorts of plants will grow there.

I also suggest talking to them about a soil test. Your soil may be too acidic, too basic, or almost sterile from the stuff that was dumped in your yard. This is rather common as developers use the property to dispose of almost everything rather than taking it to a landfill. It is also common for new housing developments to be built on top of old dump sites that existed long before the land was incorporated.

There is something truly nasty about digging up garbage. You have my sympathy, indeed.

It sounds that your heart is craving trees and your yard is saying 'I'm too wounded to respond just yet.'

The real hassle, for me, is having to wait like Goldilocks until the soil is 'just right' for digging. And, when I do, it has all the appeal of sticky play doh. Yet I need to break the plough pan and compaction as cautiously as I can. Do you have some sort of iron pan or compaction layer that may be adding to your grief? A leftover from the Ice Age, perhaps? Field drains may be the long term answer when the bank balance is smiley again.

My soil is definitely acid. It grows beautiful Bellis, Rumex, Cyperus and Juncus. It stays visibly wet for days after the last rain drop.

Looking at your list of amendments - I don't think they're bulky enough to do you any good. I'm using bulk rough compost, horse manure (NOT steer because it's too silky. I'd use that on a hungry and sandy soil.) and as much green/brown roughly chopped mulch material as I can gather, scavenge, or scrounge. Even the remains of hay bales, corn straw... whatever is slow to break down and will keep the surface safe over winter and summer.

On my soil (peat and podzol) it's safe to use shingle and sharp sand that's larger than 'builders' sand'. I know from experience I'll have to use gloves when I do a lot of weeding because there'll be an added abrasiveness in the soil. I think it's worth it, though.

If those trees are 'gotta have' - plant on a serious mound and use clean soil. You might want to check out hugelkultur on YouTube, too. It could give you the drainage you're after. It's not orthodox backyard architecture, for sure - yet it could be an appropriate land-healing step to take in your situation. I'm still flirting with it at this point.

If trees and shrubs are rot prone at present are there perennials you could use to make the upheaval look a lot more appealing? Iris ensata and pseudacorus come to mind as they are damp tolerant and would be fine in your zone. Acorus would also be worth a try. If you could keep it under control (mwahahaha!!!) you could try a patch of Ranunculus repens - so long as it's not a weed in your area. It has great roots for breaking through compacted clug. Blueberries on mounds could also be a foundation and dual-purpose planting - little feasts...:-)) Mimulus is also a possibility but it may only be annual for you. Might overwinter, if protected.

In short - do find out whether your soil is acid-trending (pH5.5 and below), or concrete-forming alkaline (pH 9 and above).

See if your local roadside maintenance people offer bulk mulch at reasonable rates and any local sawmills provide coarse untreated sawdust. Mix with horse manure and spread to at least four inches depth. Let it quietly rot. Remove any attempts by some shrubs to start wildly sprouting from the mulched pieces (willow and hydrangea come to mind).

Stay OFF the ground after rain/snow - or install all weather paths or board-walks. It just won't take even the lightest compaction at this point.

Check whether you're coping with some sort of hard pan zone below the surface.

Rethink your garden design to cope with the reality of an undulating yard rather than a conventional smooth one.

Good luck. And keep piling in the compost/mulch every year. It's worth doing.