1. I personally don't like that substrate as much as the noncompressed "jungle earth(iirc). The reason is because it contains a lot of sand, and scratchy fine fibres. When I've used it before, luckily it caused no problems for the frog that I knew of. However it reminded me of working with fiberglass to a much lesser degree.
2. I prefer the exo-terra heat matts. The design doesn't cause the connector to try to pull the heat pad off, and the adhesive is the stickiest I've tried. You should look for one that fits the largest area, for better heat dissipation. Somewhere from 16-25W(depending on the temperature of the area you put the terrarium. Controlling the heat a thermostat. I use an inkbird thermostat, I haven't got any complaints about it. They aren't very expensive.
3. Your water conditioner will likely be fine, as long as it dechlorinates water. Though reverse osmosis is ideal.
4. The crickets from your local stores will be fine. Try to "guttload" them first, and use a calcium+D3 supplement, and a multivitamin, alternating between them when you feed. A varied diet is good. I find nightcrawlers keep longest(weeks in the fridge) crickets seem to die regardless of care. However they are a great option for a growing pacman. Try to feed less chitinous creatures, as it can potentially impact their bowels. IE mealworms. Mice when the frog is large enough are a good occasional treat, high in vitamins and protein, but also high in mammalian fats, which if fed too often, can damage the frog's liver and cause blindness not unsimilar to cataracts. This is because the mammalian fats are hard to break down.
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