How to use an ESP32, a digital potentiometer, and a MOSFET+optoisolator board to remotely control a 3–5.5 V, 50–100 µA circuit?

I’m trying to add remote control to an existing low-power circuit.

Between two contacts (labeled 6 and 7 in my schematic), there’s a voltage ranging from 3 V to 5.5 V and a current between 50 µA and 100 µA.

I’d like to:

1. Remotely close/open the connection between those two contacts (like a switch), and
2. Remotely adjust a resistance between them using a digital potentiometer.

Specifically this is intended to control the switch to lower the setpoint in a thermostat (see pin 6 and 7 of the thermostat schematic). I'm thinking to replace R19 with a lower value R and add the dig pot in order to remotely control the setpoint.

I have the following components available:

• ESP32 (NodeMCU-32S)
• Digital potentiometer (MCP4011)
• MOSFET board with optoisolator (PC817) and IRL7843 transistor

Here’s my current schematic:

My plan is:

• Use the digital potentiometer (MCP4011) to vary the resistance, and
• Use the MOSFET + optoisolator board as an electronic switch, both controlled by the ESP32.

Questions:

1. Does this design make sense for such a low-current (50–100 µA) circuit?
2. Would the MOSFET’s leakage current or optoisolator voltage drop significantly affect the behavior between pins 6 and 7?
3. Is there a better or simpler way to achieve both remote switching and variable resistance using what I have?