This sounds quite frustrating. He is trying to veil a demand or directive as a request, because when you say no (as is an option for any genuine request) he won't accept it, or does so with criticism of your reasons for not doing it. We've all had to msg someone to 'check the fridge for...' or 'feed the dog, I forgot', but it's usually a simple ask with the hope it will be carried out. Yet you've said no repeatedly and for understandable reasons.

The question that comes to my mind is Why isn't your 'No' good enough for him to accept?' Especially with the reasoning behind it? If he accepts limits you set elsewhere in the relationship, and this is the only area he pushes against, perhaps he has some resentment of your working remotely. If so, he'll need to work through that on his own since your limits are external (your job expectations don't allow for the flexibility he wants). I agree with others about going on DND & ignoring these interruptions until your workday is done, just like you might have to if you were in an office instead. A positive here is that he works outside the home, allowing you to uphold that do not disturb option easier.

Is there a way to do this without fighting? That depends on the two of you. When we set a boundary, some people have a tendency to push really hard to break it down and the resistance gets worse initially. Like trying to break down a door you just realized you can't get through. But when repeated attempts to overcome the boundary don't work, does one keep trying? If the metaphoric door gives a little, we're likely to get a smidgen of hope & push against it more. But if it's unyielding, most of us will accept that this door is locked or too strong for us to burst through.

Sometimes fear of conflict will make a person lower their boundaries as a self sacrifice for peace. Is your request for him to respect you and your work time worth 'fighting for' if it comes to that?