You mentioned using a Neem based spray. In San Bernadino in summer, I'd spray late in the evening. Neem oil can burn the leaves during hot weather. Perhaps the sudden wilting is due in part to the spray.
In all likelyhood, as Kay said, lack of water may be the culprit. The pot isway too small for that size plant. If the plant has been in the same pot and soil for over a year, it is also root bound. You will need to loosen the roots on the outside of the rootball, get rid of some of the old soil by immersing the rootball in a bucket of water and use a plunging action to loosen and remove some of the soil. Spread the roots out into the fresh potting mix as you fill the new pot. Placing some of the roots well into the new soil helps the roots spread into the new soil faster. Having roots in the new soil also helps draw water from it so the soil doesn't stay wet for too long which could lead to root rot. Keep the newly potted plant in shade or filtered sunlight until it has recovered.
I may be mistaken, but the soil the Brug is in looks like garden soil, something that should not be used in a pot. It creates all kinds of problems.
That wall may be contributing to the Brug's problem. All that reflected heat only increases the stress on the Brug. It may help keep the Brug warm during winter, especially if you leave it outside, but it doesn't need that extra heat during the summer.
