Do not have an abortion in these circumstances. Just do NOT.
It's hard enough having a termination when you think it's for the best yourself.
It's hard enough having a termination when you know you've completed your family.
It's hard enough having a termination when you have massive unchangeable reasons, not 'well it could work' ones like finances.
To have a termination you're being pressured into, when you know that although it's not ideal it would be workable, and when you plan to have another child anyway just not yet - just do not, just DO NOT.
You are absolutely asking for lifelong regret and letting the kind of recrimination into your relationship which could very easily wreck it, permanently. NEVER have a termination to please someone else. It's not livable with. You will very, very likely end up resenting him for ever and possibly splitting up. Or, living with something eating away at you which will ensure that if you do stay together, it's neither a happy home nor a happy parent that your existing children will have... and god help your mental health if you DO then go on to have a baby at a time that pleases him.
Just don't do it.
The killer punch of course is that you plan to have another child anyway. So, you could end up literally wrecking your marriage and ALL future plans just in order to not 'spoil' the existing plan by it needing to be tweaked.
You also plan to train for a career - given that, and ESPECIALLY the career itself (maternity) - it's even worse an idea. A lot of people would argue that if you're planning on another child anyway, grit your teeth and get the baby stage permanently out of the way. Yes it's hard, but just do it - then go on to train and qualify without having to stop-start. Also, getting all the baby years out of the way in one go SAVES you money, as there's a fair chance your maternity will also cover a significant chunk of toddler years that you'd otherwise end up paying for some childcare for.
Add on to that that having a termination would put a bomb in the path of you feeling able to train as a doula/midwife - good lord, do you need ANY more practical reasons why it's a terrible idea to terminate?!
It's understandable that he's panicking. But sit him down and tell him - first, having a termination isn't going to 'solve' this. You won't go back to before. You'll go forward to a new phase where something absolutely awful HAS happened within your relationship and the new big question for you possibly won't be 'how do we improve our finances' but 'are we going to divorce because I can't get past you pressurising me into an abortion'.
Secondly, in a practical sense, it's a bad decision. Firstly as per above - better a third child in not-ideal circumstances than potentially a messy awful divorce and shattered finances and home. Secondly, if a third was on the cards, a huge % of people would say, get it out of the way NOW, don't wait - it won't actually help you financially in the long run, you just slow down your progress for longer really. Thirdly, you want to train as a doula/midwife and post-abortion, it's likely you won't be able to handle it. Fourth - tell him to look up the cost of counselling long-term... because that's the kind of situation having a termination you do not want puts you into .That ain't cheap either...
Hopefully he's just panicking.
But for fuck's sake don't have an abortion in these circumstances.