So when locating the ball valve, drill between the holes in the bottom of the keg, otherwise the heat from the burners will go straight up and hit the valve / fitting. Also go as low as you can, otherwise your chiller won't sit as low as you'd like it to. On the ball valve, I have a 1/2 NPT pipe nipple that goes through the keg and into a Female union. To seal the hole, I have O-rings and large stainless washers. I checked the oring recently after a few brews and it's taken a set, but still seals. If I find a higher temp o-ring I'll swap them, but they aren't melting at this point.
Since this is a short pipe, you should sweat all the fittings at the same time, or you will undo your previous work.
False bottom installed. It will lift up until it hits the 90 ftg, which is nice for cleaning.