What is getting hot. The 3-pin part in the middle or the metal square.The metal square gets rather warm, and this is normal.Warmer in access point mode than in station mode (depending on router settings).Only cold in deep sleep.Leo..
You could post a circuit diagram, showing how everything is connected, so we can check.And a links to the Oled and sensors.Leo..
Diagram look Ok.As said, you only need 5volt on V-in.Anything higher is only heating up that LDO more.Why that 8.5volt supply. Existing supply, batteries?If you HAVE to use it, then a buck converter is the coolest way.You can even step directly with that to 3.3volt e.g. with this one.
Next time, connect the switches between pin and ground, without external resistors.Use the internal pull up resistors in pinMode: pinMode(switchPin, INPUT_PULLUP);Invert all switch logic (HIGH becomes LOW, and LOW becomes HIGH).Leo..
We know about the ESP module (80mA), but we still don't know how much that Oled is using.Leo..
The Adafruit site mentions an average current draw of 20mA for that Oled.Leo..