ESP controlled soldering iron - schematics review

[Thomas07]

Hello,
Iam currently working on a soldering station. I want to use an JBC T245 and design the PCB to controll it myself.
Everything will be controlled by an ESP8266EX.

Here are the core features:

• USB-C powered (CH224K for 20V, Iam using an 100W PSU)
• Heater controlled by mosfet (AOD403 P-Channel, BC847 for driver, PWM)
• Temperature measurement by MAX6675 (K-type)
• Current measurement with 5mΩ Shunt + COSINA1803 (Amplifier)
  
• OLED-Display & Rotary encoder (KY-040)
• Sensing if the iron is in the station by an metal-ring (GND) on the iron that will pull down a pin
• PCB-antenna (not really necessary but I want to try implementing it
• I/O-Expander (PC8574), I could use a Microcontroller with more GPIOs but i figured it would also be nice to try using an expander

This is my first project using an ESP8266EX, I have done one were I used an ESP8266 WiFi-Module and CH340C chip for data.
Since this is the second forum I post this project I got a lot of feedback already, so I want to clearify a few points some people misunderstood:

• A lot of people critisised my schematics and the legibility of them. I learned it like that in school, I dont know how to do it better. So please tell me what to improve and not only that there are bad (thats the only thing I got told in the other forum).
• Some people also wondered why I would need WiFi-abilities with an soldering iron. I just want to clearify that I am doing this just for the purpose of education. I want to learn how to design PCB-Antennas, impedance matching etc.

Now the things that got mentioned in the other forum and Iam not sure about:

• Mosfet - P-channel configuration

I got told that I have to pull-up the Gate pin of the Mosfet to 20V (I had it at 5V before). That makes sense because then the gate-source voltage will be 0V and the mosfet won't conduct. But Iam not sure about that resistors and their values. I also heard that I should add an 100Ω resistor to the gate to limit the current. I dont know if its necassary, I would like to keep the design as simple as possible, but if its really necassary Iam going to add it obviously.

• I/O expander and Rotary

I was not sure about it and I also got told that it may be ambitious to read the rotary through a I/O expander without using the Interrupt pin. Iam not sure because it will only be an knob for the menu, but I really can't imagine if thats possible or not. Would it be easily possible with using the Interrupt pin, or would the delay of I2C still make it hard to get a clean output of the rotary?

• Thermocouple

Someone said that the thermocouple in the JCB Iron isn't an type K. In the video below:

the creator says that a type-k circuit delivers acceptable values, since I dont need the best accuracy, Iam not sure if it would be okay to just use an MAX6675 or if the values will be completly wrong then.

With that said, Iam happy for every tips for improvment. You can also tell me how I wrote this "article". This is probably the second or third time posting something in a forum, so Iam not that experienced.
In the attachment you find my schematics.