1. Like to use the ramp type water bowls made by ZooMed and others.
2. Give a 2.5 in. Pacman all the food it will eat to satiation once daily. When it reaches around 3.5 in. will be eating lots more and you might notice a less enthusiastic feeding response. That's your signal to feed every other day.
3. No, EcoEarth and Plantation Soil should pass through digestive system with no problems. Think a bit of it is even good if feeding night crawlers only as it provides roughage.
4. I don't feed Pacmans' in containers due to handling and stress involved. Imagine over a damp towel is best option if doing so. The supplements that fall of worm into paper towel should be of little to no concern. Again, not an issue if you feed frog in it's enclosure. Good luck !