Cut is down and in about 10 to 15 years the juglone will be gone and you'll be good! Takes that long for the massive root system to rot.

I might biostimulate the area by spraying dilute molasses over the rootzone and then watering it in before a rain.

Actually some say as little as a year and it will be gone. I think it depends on how fast the roots die. A good way is to kill the roots with roundup first. Although all parts of the tree produce juglone, the roots are what usually remain so killing them first makes sense. I hate to kill any trees though. I'm glad I'm not faced with such an issue.
If you have an objection to using roundup, any other way to take out the roots would work. Even if you do nothing, my statement is probably way off. It seems it depends on environmental conditions on how much the juglone expresses itself. And who knows what to believe? I have heard 15 years to one year, so the jury is still out on this one.

I'll be hookng up the 3" caliper seedlings to a chain and pulling them out by truck.