I don't know any Dutch employment law but bullying is bullying in any language. he is forcing you to work when you are off sick. You could take out a grievance against him for bullying you. Threaten him. tell him he is making your condition worse and that you will take out a grievance. Apologies if I've missed this in your post but do you have the option of having an Occupational Health assessment. I would ask for one which may tell your boss to leave you alone.
And talk to your Union rep. Get them to speak to your boss on your behalf.
Apologies if none of this is relevant.
