If you're on a low income you will get tax credits as well. Try this site to see what you might get. It may give you enough of a breathing space to work out what to do.
Yes, your DH needs to wise up. If he's job-hunting himself he can hardly tackle you - who has a job - for not being ambitious enough. And if it's so easy, why hasn't he found a better job himself? I think his frustration at not being able to find another job is probably the main reason for him heaping this on you.
That said, I think it's lovely that he sees you as worth so much more. It's worth thinking about it. We still live in a man's world when it comes to employment. More men are in top jobs than women, there's still a pay gap, and men are still socialised to consider ambition a good thing while women are still socialised to consider work secondary to their family's needs, which inevitably includes working crappy jobs to provide for basic needs. I know that's a massive generalisation but it's surprising how often it applies.
For men there is so much self-worth tied up in providing for your family, which many feel is best measured by how much you earn. In this case, he's transferred that on to you as well. It doesn't mean he's sexist BTW it just means that he and you have different perspectives about 'providing' which are based on our cultural norms and are different for each gender (if the same messages were sent, we'd see a much more equal split of childcare responsibilities and income by gender). He probably doesn't realise how much harder for you it will be to move into a higher paid job simply because you are a woman because he has never been a woman and a lot of the stuff that makes it harder for women is very, very subtle.
Out of interest, what would happen to the baby if you work full-time. Does he see himself as a SAHD? What would happen if he found another job? Would he expect his job to take priority in terms of who takes a day off when the baby is ill, etc?
It's horrible that you're having to stress about this while on ML. This is the time you should be enjoying family life. I really feel for you. I think all you can do here though is keep on talking and do your best to understand each other's POV even if you don't agree with it. You need to pull together rather than against each other. Good luck with the job hunting.