For both species 95 is too hot AND 70-75 is too cold. BPs and boas ideally have a minimum temperature of 78-80. 75 being the absolute minimum. And advised against as low temps lead to lower immune response and can result in infections.
Boas especially prefer higher humidity 60% at least all the time, and most BPs do better shedding when kept around 60% instead of 50%.
With cleanup crew, I doubt mold will be a big issue. But if it is an issue, that's a sign that your spot cleaning failed to pick up all of the waste and gave it "food" to grow if it is happening within 1 month or so. In non-bioactive tubs, I've yet to have mold up to 2.5-3 months with eco earth or reptile prime coco fiber products. I'd also bake peat prior to use depending on your source.
The tiny white specks you see in the tarantula cage I would guess are most likely either wood mites from a nursery/hardware store source of the substrate. Since you have springtails, I assume you can tell the difference otherwise that would be my second guess without a picture.
The boa is likely not eating due to being too cold, if I had to guess. Especially if he/she is hanging out on the cold end of the enclosure at those temperatures.
Also, definitely do not put the heat mat INSIDE the enclosure for any reason. They're called "Under Tank Heaters" for a reason... they go under the tank. Thermostat probe typically goes between the heat mat and bottom glass or plastic of the enclosure to measure and regulate the temps.
Keeping one inside the enclosure is a huge electrical risk for most brands are they're not submersible and being submerged in snake pee or spilled water definitely can damage them and maybe even cause an electrical short. Not even counting that a big pee or water bowl puddle would cause the thermostat to read incorrectly and might spike the temperature.
Under the warm hide, put a thinner layer of substrate than the rest or keep a thinner layer of substrate overall so the heat can penetrate better.
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