It's all well and good people getting outraged on your behalf here (and totally understandable) but that isn't going to help you.
It sounds like you are going to half to take the high road here - you need to sit down with him and actually talk about this. Not get into a slanging match, but stay clam and keep the conversation going, even if that means having to sit there whilst he lets out his frustration for a bit. Is that fair? Well no not really, but it's what needs to be done.
It would be unhelpful to go in saying "I'm keeping this baby but..." don't mention that. You need to understand why he is reacting like this, and going in on the offense won't help.
Maybe open with "I need to understand your reasons behind your reaction to this pregnancy. I know you aren't happy with it, and I know you don't want it to continue, but I need to understand why."
If he gets pissy or snappy, or walks away stay calm, but say "Getting angry isn't going to get us anywhere. It isn't going to change anything".
You mentioned he panicked about having to move at the beginning - could that be part of the reason behind his reaction? The thought of having to up and move, up rooting your existing family, the stress and money involved, that sort of thing? Do you work? Could he be worried about finances? Could you suggest that you start working part time to help with the household costs (assuming you don't work)?
You can only talk through practical issues when you know the ones he is worrying about.
Likewise, when you had your abortion a while ago, did you ever tell him how much it affected you? When you have spent a while talking about his side of things, you need to raise this in a non aggressive way. You aren't speaking from thoughts about how you MIGHT feel - you are talking from experience. Likewise, your situations are different not - back then you barely knew each other and were probably in a different situation life wise. But now you are a married unit - you have other children, there aren't the same life reasons to do it again. He might be thinking if you did it once, then you would be willing to do it again.
Also, I think many men have a different attitude to pregnancy than women - the pregnancy is a potential - it isn't something that has happened yet, as the baby isn't there and all sorts can and do happen in early pregnancy. To many women, it is something that has happened already. The fact the pregnancy hasn't finished yet is sort of a by product. He needs to understand that this isn't something that can be just swept under the carpet.
You cannot lose your temper during this discussion. You just can't. It might be frustrating, but you have to look at the bigger picture here. You both need to understand the other persons' rational. You might be able to come to an agreement. You might not. But you have to behave like adults and discuss it properly, even if he is behaving like a total and utter brat.