Probably auto-buddered from the heat and moisture content. Moisture content might be a little higher due to blasting in warmer temps with high humidity.
Frankly 4 hoods is a little beyond capabilities of a 6" single run in series.
Probably best to put 2 parallel runs, each consisting of two 6" hoods into an 8" trunk and run an 8" centrifugal blower.
I prefer domeless titanium nails, much harder to swamp with big dabs, hard to crack too. KO Domeless version 2 is nice.
Stainless dabbers or titanium is ok but not required for the dabber. I hate glass ones, too fat, much waste when wiping off the junk post dab.
Garbage In Garbage Out
Computer lingo that very much applies to concentrates.
Start with quality product and the results have the potential to be quality provided the extraction process is properly performed.
It is recycling your air indeed.
With occupants and shared environment I don't see any need for worry unless your grow is more than 4kW ish. Usually ambient co2 in a home is higher than outdoors.
It does more harm than good when people berate those disseminating truth. In fact it's often why those with truth to share just say "fuck it" because they realize in advance what contradictory nonsense some blowhard will post immediately thereafter.
Chart here quantifies time vs. temperature.
http://skunkpharmresearch.com/decarboxylation/
When cooking, especially baking, how long is the inner part of the food at full oven temperature?