About one hour and 1.5meters of heater wire later:
Excellent! The second lowest setting gives nice and toasty+38C temperature.
(The second highest setting gives +85C... Crispy?)
That means I can lower the pwm frequency and get the highest temperature down to +40C and that way there will be more precise temperature control. (Don't worry if you don't understand. Neither do I...)
Calculated heating power is about 10 watts. Tomorrow I will do the other glove and set them to be in series, that will lower the total power to 5 watts. Should be enough and that will also keep current draw in around 0.4 amps.
If all goes well, I will perform field test on saturday. Weather forecast says it will be a cold day. Just above freezing in the morning. Perfect weather for testing.