First mistake was using the old planer blades for something to be forged. O1 or even OCS(Old Chevy Spring) would probably have been a better choice. At this point, I'd cut the tangs off, they're going to be too brittle to stand up and will be unbendable, and braze on some low-carbon rod stock for your tangs. HSS or D2 is not something you can anneal at home successfully and then reharden. It's not like carbon steel at all, you can't just heat it up red hot, slowly cool and soften it up. This would probably have been a good application for high-carbon steel differentially hardened, hard cutting edge, soft back and tangs. Or you could have brazed a cutting edge onto a low- carbon body. You've gone this far, though, see how well what you have works.
Stan