Why don't you tell him about the miscarriage?
Whilst I suppose you wouldn't feel happy about becoming a mother again in your late forties, miscarriages take their toll on women both physically and emotionally. And now you are keeping all this distress to yourself.
You shared your body with him and he helped form this potential baby. If you tell him, he has the chance to comfort you. You could make it clear that you are not telling him to make him feel guilty, but that after debating the pros and cons you thought he might want to know what you've had to go through.
I know you are anxious to preserve your dignity and self-respect and feel any move has to come from him. But he is now not in full possession of the facts. And as you say, the hormonal disruption has caused you to be more irascible than usual. If that has pissed him off, he ought to be told the circumstances.
As to the 'boxed off' issue, I don't really know. Relationships in middle-age can be complex, and there is often a mismatch between the wishes and expectations of the two parties.
My DSis was widowed in her late forties and began a relationship with another man a couple of years later. She did love him, I think, but whilst his greatest desire was to marry her or at least live with her she wasn't interested. She said she wanted her own space and never wanted to live with a man again. It was a bone of contention, and they'd regularly argue about it until he unfortunately died suddenly.
I know this is not quite the same issue as yours - I just wanted to illustrate that these mature relationships are often fraught.
The passion and warmth of your feelings for this man glow from your posts. I know you're not happy about the compartmentalisation, but is it so fundamentally important? I suppose it must be for you since it's been a deal-breaker. You seem so very sad, though.
Btw, I'm another home-worker who often feels isolated, even though I've always been one who enjoys her own company. Also, I had two very close friends from childhood; one died at Christmas and the other has had to move away to look after her elderly parents. I feel bereft. Lots of loneliness about.
Don't know how you can say you are old when you're not even fifty though. I'm almost fifty-seven and am still a total babe. I know because DH tells me so (he knows what's good for him, and is also very short-sighted).