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You know, I've been puzzling and puzzling over your post, and while most of it doesn't make sense to me, I think I may have come to understand the root of your problem.

You aren't so much concerned with how the heavy elements get created, but with how they got scraped back up together again to form our solar system. Right?

If that is your concern, you may be interested in this calculation I performed almost six years ago on FR.

Here's the executive summary: given a cloud of arbitrary size that has a density as low as any found in the galaxy (one hydrogen molecule per cubic centimeter), how long does it take for the cloud to collapse completely? The answer is 700,000 years. Less than a million years. A cosmological eyeblink. Denser clouds will collapse even faster.

So if you have a supernova going off every 30 years or so, let them spread their heavy nuclei as thinly as you like across the galaxy. Gravity will have no problem collecting them up again in a very short time, whenever it has the chance. All it takes is a local density fluctuation to start the process, and the trace residues of a million supernovae--now evenly spread throughout the galaxy--will condense to form a solar system.

Another suggested Google search term: Jeans Instability