Family Code 2623 requires that debts incurred after separation but before entry of judgment of dissolution for "nonnecessaries" of life, must be confirmed "without offset" to the spouse who incurred the debt.
Given that you and your spouse each incurred the cost of sale (a nonnecessary, in my opinion, but reasonable minds may differ), each of you would have a one half share of the debt, regardless of your interest in the property.
However, Family Code 2625 requires that debts not incurred for the benefit of the community must be confirmed "without offset" to the spouse who incurred the debt.
So, the question is, did you incur a separate debt, for your separate interest in the property, and did you and your spouse each incur a joint debt for the community interest in the property -- or, was this a single debt incurred by each of you for the entire sale.
If the former analysis holds, then you would owe for the percentage of separate property, plus one half of the percentage of community property
. If the later analysis holds, then the transaction would be a pure 50/50 split.
I have search California appellate case law and I am surprised to find no case on point to your concern. The closest case that I can find is IN RE MARRIAGE OF BELL (1996) 49 Cal. App. 4th 300, in which the California Court of Appeals determined that because the community property of spouses was increased by one spouse's embezzlement of funds from her employer, that the value of this ill-gotten gain must be divided 50/50 -- but that the bad-acting spouse would be separately liable for any debts incurred as the result of her wrongful conduct.
Applying this case to your circumstances, it appears within the court's discretion to apportion debts incurred according to the underlying property interests, but not to divide community property in a manner other than 50/50.
Considering the possible cost of litigating this matter to conclusion in an appellate court, you must make the choice of whether or not to fight. Family Court, at its base is still considered a court of "equity" (fairness), despite the reality that the state legislature has effectively removed practically all discretion from family court judges (a fact that the same judges tend to ignore daily) -- so, I think it's highly likely that the first analysis, where the cost of sale is apportioned based upon the parties' respective interests in the property, would be the court's ruling -- because there simply isn't anything in statute or case law to prevent such a ruling.
A very interesting question, to be sure. Thanks for offering it here.
Hope this helps.