I can sympathise with both sides. On the one hand you are heavily pregnant and have a busy life with house guests and a toddler, as well as your own health problems to contend with.
On the other hand, your landlord is probably losing sleep over how he will afford to pay the mortgage and bills on an empty property with no income from it as well as all the costs of his current home.
In between tenancies on my flat, I am always so grateful to tenants who clearly do their best to help me out with viewings, and have felt let down. by those who say I can show people round once a week. Not everyone who is keen to see the property can view it on the designated day and it can delay things horribly for no good reason.
I suppose I have always pride myself on the fact that I repair things immediately as though I still live there, and have always made concessions where I can at a tenants request.
However the law does say a landlord can enter a property if they give 24 hr notice with tenants consent, or immediately in an emergency. It is commonplace for contracts to state you WILL give reasonable access for viewings to re let or sell the property. If you've signed that contract you are guilty of breaching it if you aren't allowing reasonable access. However the landlord can only enforce it by way of court and that takes time.
Like I said I can see both sides. In an ideal world the landlord would have considered your estate agent preference if they were quite rude (but did he know this?) and would meet you halfway regarding painting and photos, and visits of viewings.
But, inconvenient as it it, I think it's reasonable for you to try and meet him half way too, so maybe as for the painting to be done in 3 weeks as it would be much easier to do when he property is empty, but also offer a few various times of viewings and maybe go out at those times so no one is disturbed? That way your visitors can be free to enjoy their stay with you, and you don't have to sniff paint all day long! But your landlord can see you're both meeting somewhere in the middle.