I'm working on a similar blade and am encountering a similar problem. The simple answer is, keep grinding. If there's enough metal left in the blade, just grind down to the finished size and shape that exists within your blank.
For my own knife, after investing a considerable amount of time in trying to flatten it post-hardening, I am about to re-anneal it, file it flat, and harden again. I'm regretting the loss of time (and sandpaper) invested, but without a proper knifemaking grinder, it's really my own best option. Don't be afraid to fall back and retrench, if necessary.