Critter, I do not recommend vermiculite for succulents, it retains more moisture. It is suitable for water loving plants, not for succulents that prefers to go dry faster. Perlite,and pumice will be better to add in your soil mix.
Delosperma seems to prefer really less soil as media, make it rocky, sandy and very porous, no fertilizer and full sun. It is not good indoors, it really loves the cool sun, same conditions as semps.
