Oh what I mean is this, a solution that might seem fair, doesn’t necessarily mean it will be well received by all. If one person feels like they got the bad end of the deal, the person may just wait for the right time, and pull out the exact same argument against a purchase made by the other. Also possible is just to wait, try to get back the person in another way. If anything, even if it doesn’t lead to anything directly bad, it can lead indirectly to stain in the relationship.
A seemingly fair arrangement isn’t near as important as an arrangement that both are comfortable with and are relatively happy with. Part of that may be due to the terms of the arrangement, and another part is due to how the arrangement is made. Sometimes you cannot get there, and you’ll have to pick your battles wisely; some battles are not worth it, and some are essential.
The way I see it there are two different battles going on: one is just the straight financial aspect of it, and second deals with the feeling of security or insecurity of your financial footing. Personally I think both ought to be addressed, but it is best to avoid mixing the two at the same time. I’m guessing if you mix the logic of finances with the emotion of security, you both will end up upset. The money is not worth the strife, but you do need the money for security and stability.
I’m guessing if he starts to think your going to be arguing that he is “an impulsive, irrational idiot” it with money I doubt you’re going to get anywhere good. I don’t think you should not deny you are upset, that’s perfectly justifiable – you can feel how ever you want. You just don’t want your feelings to sabotage a solution. They do point you to something that needs to be addressed, but if someone feels emotionally blackmailed the relationship is strained.
On the financial front, you might do well to point out the econmic impact it will have on the family, and look at the options. It is also important to address at another time, both of your outlooks towards towards money. If you understand that if a few things happens you could easily get behind, that certainly is a justifiable reason to feel insecure. In that sense, you can help encourage him what steps he ought to do for good money managment. If you have an option between a postive approach (what to do) and a negative appraoch (what not to do), the postive approach should go better in a persuasive situation. You can understand better how he feels about it. In the end that ought, then you understand better how the other will take a situation, what battles to fight and avoid, and just a better understanding of what is acceptable.