I have mixed molasses and white sugar before when in a bind, but it's not particularly easy and the baked goods never turned out tasting the same. Great idea for storage, but I wouldn't use it on a normal occasion so it violates my rule of store what I eat and eat what I store.

Some things I have read say just don't use an O2 absorber like the advice you were given at the LDS place. That's why I'm worried I've done it wrong. However, I bought a #10 can of brown sugar (I think it was Augason Farms or Provident Pantry) and it had an O2 pack inside.
It's not a lot of money if I decide to throw it all out. I just hate to do that if it's not bad. But unless someone else can tell me they've stored it with O2 packs and didn't later die, I think that's just what I'll do to be safe.