Just to chronicle progress for future searchers, Now I have the 2 separated elements on the work table. I'm finding it strange that while acetone was ineffective at separating them and that methylene chloride (DCM) was what did the job, just the opposite on cleaning the residue. Soaking pieces of cotton with DCM, did practically nothing at scrubbing the glue residue off the face of the glass. Acetone seems much more effective at that. I have both elements clean now. I will go over then again, then do the standard Q-tip and cotton swab lens cleaning, and proceed with the balsam gum. So far, so good--no damage done.