Fireworks – comfort him or leave him his space

I'll go straight to the point:

When my dog hears fireworks he hides in the bathroom. I'm not sure if I should just leave him be, if I should sit in there with him, or if I should do something else.

He'll sit there trembling for hours. For me to sit there with him would be hard – I have to wake up in the morning and he'll easily sit there until 3 or 4am – but I could lay down an air mattress and sleep there if need be. During these episodes h won't take treats, seems to get more worked up when we touch him and just seems to be 100% dealing with his anxiety and fear.

And yes, we're working on desensitization, but due to how sensitive he is, we still have a long, long road ahead. We started with small firework sounds on our speakers months ago and still can't turn up the volume. He goes straight into trembling and won't respond to anything. At most, he'll spend hours and hours wandering around the house.