You're mixing your fruits and your vegetables. Obama has no control over his mother's pleadings in a foreign court, much less a foreign family court over matters of financial responsibility for adopted children (minor children or adult children), even if those pleadings go to financial burdens that surround his own educational needs. I would say that whatever Stanely Ann Dunham claimed in divorce proceedings would be irrelevant to Obama's status as a US citizen.
I don't know if he entered Occidental as a "foreign" citizen, as you proclaim. It's possible, but I haven't seen any proof that would substantiate that claim. If he did do that, it could be taken as a voluntary renunciation of his US citizenship. I say could because I'm not familiar with the specific case law with respect to this issue, and the statute that governs loss of nationality, Title 8 § 1481, doesn't address this particular circumstance.
Having said that, it should be understood that the US recognizes, albeit only through silence on the matter, dual citizenship. US law doesn't mention it specifically, but State Department regulations are written to accommodate people with dual citizenship claims. And, these State Department rules would perhaps be informative in this case. I would think however, people who did claim dual citizenship, either actively or passively, would be forfeiting their right to claim the status of "natural-born" citizen. But, it's only an opinion.
Your effort to twist the issue to suit whatever you have as your chosen perspective for whatever reason is duly noted. What Barry's parents did prior to his reaching 'after turning eighteen' is not the issue, his use of Indonesian citizenship in entering Occidental is the issue because if he went in as Barry Soetoro he used his Indonesian citizenship over American citizenship as an adult not a minor child.