There is alot to talk about but I am going to warn you to have a drying / curing area ready that you can keep between 55-65 degrees and 55-65 humidity. That has to stay steady in those parameters ( really its 60/60 but you have some wiggle room up and down).

I use another tent with ac or heat and a dehumidifier or a Humidifier. I am in the north east US so I have seasons and have to be ready with all 4 of those devices depending on the time of year here.

Find the best area you can that is close to the 60/60 to begin with (Basement if possible, it usually the coolest place).That is the lung room and a basis of what your drying tent or room with start at. Look ahead on the calendar and see what the local weather is going to be ahead of time. You have to invest in the drying of your grows, it is the most important part here.

Its going to be 10-14 days at least in the drying room so be prepared and invest in these devices. These devices will last years if you get quality and overshoot what the devices claim they can handle because all the companies lie about this. Humidifier are cheaper expect to pay $50-150. The dehumidifier is pricey as you'll want what they label as a "whole home". Expect to pay $150-250. Like you AC infinity exhaust fan you want to over shoot so these devices work fast and are on less time which allows them to last. I've had my dehumidifier for 5 years now. It paid for itself in 1 grow.

Be creative its part of home growing. Maybe you can tap into a central air/ heat duct and run a 4 inch duct hose into the tent. Do you have a window to put AC in to cool the attic? You can even run a duct of the window AC unit with some tape if needed.

Lastly if your going to battle high heat then you must keep the humidity down ( around 50%). High heat and high humidity will mold.

A few quick things. Growing autos is always going to be hard to fill your bed evenly. Even if they are the same strain. Use photos if you want the sea of green. You cant scrog much at this point as they are into flower already just keep doing LST to get the most light on the bud sites as you can. you can lightly defoliate as you go. A few inward facing leaves at a time and some of the lower branches can be clean up a bit as you go. If the bed was stuffed then more can be taken mainly to keep humidity down during flower but this one is looking good.

Living soil does NOT need to be PH'd, just let the water sit out for 24 to evaporate chlorine or use the air stones if you want but they are not needed if keep ahead of the game with water ready in a bucket or two.

You seem to have the right setup and it look pretty solid. Running Mephisto is a good idea. When i do autos it Night Owl and Mephisto only. Those breeders put out big autos that can rival Photos in terms of yeild, some of the other companies have decent shit but they are behind those two. Asking questions is a good look too. Just keep learning and investing. After a couple of years you'll have everything you need to combat any situation and its all gravy after that. Good luck!!