I would suggest to develop your project using Digispark ATtiny85 Dev Board (Fig-1) with Vcc = 5V and using only one thermistor sensor at a time. After that you swicth over to 3.6V supply and tune the parameters.
Figure-1:
R4 should be 60 Ohm for a 60 mA current, but likely if you connect a multimeter to that motor you get a much lower resistance, could be as low as 10-20 Ohm.
Why is D2 there? All it does is drop 0.7V which makes your motor spin slower. If your motor is rated 3V instead of 3.6V, better use PWM to limit the current by ratio (so about 83% duty cycle, analogWrite(pin, 213)) or whatever is a good speed for you.
R2 is far too low a value, trying to draw about 70 mA from your MCU pin, which it can not deliver, hence the steep voltage drop. Make that 330-470 Ohm, that should still be enough to drive that transistor well into saturation, while limiting the current from the pin sufficiently.