carrots are good but also some spring greens, apples, romaine lettuce, watercress etc. There are commercial insect diets also available that can be added every few feedings.
i really don't like heat mats on the walls. the problem is that their primary use is to heat the substrate and glass - not the air temperature. in order to get any increase in temperature more than a couple inches away from the glass then they'd probably have to be running full blast and uncontrolled, which means 100 degree+ glass at touch, which could be dangerous should the frog make contact, but more worrying is that the mat may burn out if at full blast constantly. When the frog is burrowed it won't use heat stretching side ways across the tank, so it's not really effective. i tried this method of heating and my frog did not fare well. a heat lamp is better, your heating from top and this will be usuable. in a 10-gallon or similar sized tank it will warm and cool end, so the frog doesn't have to spend all of its time under the heat lamp.
just in one feeding, they take down large prey such as even their siblings, so can handle it. They just need warm temps and time to digest before the next meal. there's more risk of underdosing with supplements, but I like Repashy Calcium Plus above all other supplements, it's designed to be used daily. However, there's probably more supplements on the market with similar design. I've never used the ones you have so would not know their use, but you can email the company and ask what they'd recommend. In any case, with juveniles you always dust every feeding and you can get away with dusting less with adults depending on supplement, diet of your frogs and diet of your insects.
many people use commercial gutloads with their insects, which add a lot of vitamins the same as with a multivitamin supplement and so they may get away with using the supplement dust less. really, gutloading is an alternative to dusting and i personally think combing the two together could be providing too much vitamins. gutloading isn't really just feeding veggies and fruits to the crickets tho, as this does not provide all necessary vitamins. gutloading isfeeding a special made forumala to increase the calcium and vitamin content which dusting would give.