Oh dear. Your dp hasn't really got the partnership/family thing, has he? It's not even about having a 50/50 split, it's about both of you feeling that the available resources and demands (money, childcare, housework, paid work) are split in a way that you both feel is fair. In the end, once you marry or set up home, and certainly once you have children, you're not two individuals any more, you're a single unit, and however you divvy up the finances and the paid/unpaid work, it has to be a setup that both of you are reasonably happy with.
You're not alone, mousie -- there have been other posters in the past with similar arrangments, but it's not okay if one of you is left feeling that you've got the raw end of the deal, particularly if the other person is not prepared to take those feelings seriously and discuss them. If your work situation is making you really unhappy, then that is something that affects all of you as a family, and it's reasonable to expect him to sit down with you and try to come up with a more workable solution. That doesn't necessarily mean you have to live on economy baked beans and lentils (though there are circs in which that might be the least worst option), but it does mean that you should all sit down and try to work out which permutations of paid/unpaid work and more/less money are likely to fulfil the greatest good of the greatest number.
Can you try to find out which aspects of the possible changes he finds threatening? Even the most amiable men can get arsey if they feel that an aspect of life that they see as central to their identity is under threat, but they need to be gently persuaded to see that it's not a case of all or nothing, but rather that by making a few adjustments (eg. buying one or two CDs a month rather than 10 or 20) they can bring about an increase in overall family happiness without suffering too much deprivation themselves. My dh can generally be brought round by pointing out that happier wife = more and better sex.
I hope you can work something out, mousie.