We do need to be really focused and exact about bath bomb recipes in order to avoid the frustration of failure! In my numerous experiments extra oil added to the mixture has only ever led to a failure to harden. Of course if you do want extra oil in your bath it is always possible to pour it seperately into the bath. Personally I prefer the dispersing oils available as these cause less mess, and of course are also be a good carrier for essential oils. :!:
Again 1 tbsp citric, 3 tbsp bicarb, less than 1 tsp oil plus essential oils. The aromatherapy standard for essential oils in one bath is to aim for 8 drops. Of course lavender can be used in any quantity as it is one of the few which are safe to be placed directly on the skin.
I do hope we overcome these problems which have made so many of us give up on making bath bombs. It's a real shame as it seems to be purely about the spread of misinformation and bad recipes. Happy bathing!