So enclosure en temps are good so now it’s really a matter of has he been well started or not which that it never easy to tell without a record, with smaller species I tend to at least give them 10 meals before letting them go and those have to be F/T meals, obviously you also have that question of whether the animal or not was completely switch to F/T.
As far as substrate I have never be a fan of sand in captivity I use coco husk which is fine coconut bedding, I buy it by bricks pour water let them expend than dry and use them with smaller species. If/when I feed F/T I simply put the feeder on a piece of paper towel.
Now I know that it’s often not a choice and also not convenient to find live pinks unless you have a specialty store nearby and right now with everything that is going on could be even harder, but have you tried live?