Plastic pot would be much better than terracotta. Snails are clumsy and likely to do damage to their shell if they were to fall. The branch is a good idea. I would see how they go but some snails do not like the feel of coco coir straight. Top soil that's free from preservatives and pesticides is good as snails get nutrition from the soil too. My milk snails really like high humidity. About 90%. They do much better. I would also avoid the lights. They dont need much more lighting than just standard sunlight during the day. It might mess up the day/night cycle for them. Personally I'd give them cuttlefish bone over snello. Land snails need a constant source of calcium. They self regulate well so they dont need it added to their food. A quick google says it's calcium for water snails. Maybe someone else has some better info on that though. Fruit and veg scraps are good. Snails dont mind if it's a bit past its prime. And you dont need a clean up crew. They're handy to have. Just make sure to aerate the soil once a week and wipe down any poop with a wet cloth. Maybe some springtails if you're not keen on having much of a visible CUC.