OP, I have to say, I think your DH sounds as if he’s being horrible to you about this.
It’s all very well to be “very money orientated,” but life happens. It doesn’t sound as if you’re living in poverty.
Why is he convinced something will be wrong with the baby? Can I ask how old you are?
I don’t know how many weeks pregnant you are, but you need to remind your DH that this is the sibling to your current children. If he forces you to terminate, he will have to live with that for the rest of his life. Every milestone for your other two, you’ll be wondering about this baby and what might have been. Has he thought this through?
The resentment you will feel towards him is more likely to push you apart than the alternative. Chances are, he’ll accept reality once the pregnancy develops and the baby arrives and he’ll never look back. Is he fairly hands on with your current two?
There’s no way of knowing how hard it is going from two to three because it purely depends on the personality of the child. My third was a dream, but number two was far more demanding.
Yes it does mean extra rooms in hotels and larger cars, but you just adapt - eg. find places that do family rooms or have an extra pull-out sofa in the room. No drama really. The extra set of school fees is significant for sure, but I’m not sure there’s much you can do about that. Maybe if and when you come back to the UK, move to a good grammar school area if they’re reasonably academic? There’s always the chance one of them could get some kind of sports or music or whatever scholarship? You just never know!
I do wish you all the best and I’m so sorry he’s not being more supportive. He needs to think beyond the money through and remember there are more important things in life.