Facts
The spouses [B.] (wife, respondent) and [A.] (husband, appellant) married on 25 November 2016. A minor child, [C.] , born on 14 March 2011, is issued from the union. In spring 2017, the husband left the marital home; the wife has since lived there alone with the child.
On 2 May 2018, the wife seized the Tribunal de première instance of Geneva with a request for provisional measures during marriage, seeking in particular a child maintenance contribution staggered by age (CHF 6,000, CHF 6,500, then CHF 7,000 per month, family allowances not included) and a maintenance contribution of CHF 12,000 per month for herself from 1 September 2017. The husband requested a reasonable maintenance for the child of CHF 2,390 per month.
By judgment of 12 September 2018, the Tribunal set the reasonable maintenance of the child at CHF 3,500 (allowances deducted), ordered the husband to pay CHF 3,500 per month for the child and CHF 10,250 until 1 April 2019, then CHF 9,000 per month for the wife. The Tribunal had retained a hypothetical income of the wife of CHF 2,500 per month, a point that the wife did not contest on appeal.
The husband appealed on 28 September 2018, seeking in particular a child maintenance of CHF 2,700 and a reduced contribution for himself. The wife requested confirmation of the judgment.
By decision of 25 January 2019 (served on 14 February 2019), the Court of Justice of the Canton of Geneva, Civil Chamber, reformed paragraphs 6 and 7 of the judgment: child maintenance contribution of CHF 3,500 per month from entry into force, and maintenance contribution of the wife of CHF 9,053 per month until 31 March 2019, then CHF 8,241 from 1 April 2019, from entry into force of the decision. The cantonal court retained a hypothetical income of the wife of CHF 1,665 per month, based on repetitive activities in the cleaning sector.
The husband filed a civil law appeal with the Federal Supreme Court on 20 March 2019, seeking a contribution of CHF 7,890 until 31 March 2019, then CHF 6,640 from 1 April 2019, subsidiarily the remittal of the case to the cantonal authority. No observations were requested.
Main questions at issue: whether the principle of disposition (art. 58 CPC) was violated by the reduction of the hypothetical income; whether the inquisitorial maxim applicable in provisional measures was correctly applied; whether art. 8 Cst. can be invoked; whether the dental expenses alleged by the husband and the beauty expenses of the wife were assessed arbitrarily?
Considerations
On admissibility, the appeal is directed against a final decision (art. 90 FSCA) rendered on appeal by a higher authority ruling as last cantonal instance (art. 75 FSCA), in a pecuniary matrimonial matter (art. 72 para. 1 FSCA) whose amount in dispute reaches CHF 30,000 (art. 51 para. 1 let. a and para. 4, art. 74 para. 1 let. b FSCA). The appeal is admissible in principle. However, as the decision concerns provisional measures within the meaning of art. 98 FSCA, only the violation of constitutional rights may be invoked, according to the principle of allegation…