Over 3 weeks out, if anyone facing this reads this thread later, a treadmill run went OK without a sling or rib wrap. I know, you see this same question in running blogs but it's always something like "I ran a track meet 3 days later and had a personal best, winning State" etc. For an honest assessment: the collarbone didn't really hurt, ribs are sore now but not while running. No particular fatigue or joints or muscle issues. The bad news is that wind was the limiter.
I'd been running 8 minute pace for my daily 4-4.5 miles, but 9 minutes was practically threshold today, with 3 miles about all I could do. HR at threshold levels also. Whether that's due to the rib and lung injury, or just age and a few weeks off I don't know, but there is a lot of ground to make up.