To avoid stains and mold marks on the chocolate bar after hardening warm up the mold a bit with a heat gun before pouring. Also let the mold stay at a room temperature for 3-5 minutes before putting it in a fridge so crystallization will run more even.
The more water in the filling — the poorer its shelf life. If you want to get a candy with a long shelf life (4 months or more) without increasing the proportion of sugars and with no preservatives inside use fat fillings.
If water accidentally gets into the melted chocolate and it begins to thicken, you can't restore it. But you can make an excellent chocolate cream or ganache by adding warm water with constant stirring.
Infusion can be hot and cold cooking. The first one takes a minimum of time (up to 15 minutes). The second requires 10 hours or more, but such a method guarantees the conservation of all the healthy features and active components of the ingredient.