Salam aleikum, If the wife is doing voluntary fast, and the husband is not fasting and asks for oral sex performed on him, is her fast broken? Only the husband ejaculated and she tried her best not to swallow anything and spit everything.
If nothing is swallowed from oral sex, the fast does not break and also, there is no sin in breaking a voluntary fast. At any rate, the husband should tell his wife before he ejaculates so she can pull our her mouth as the semen gushes forth with force and not swallowing it may not be possible.
Also there’s nothing that I know of which forbids reciting Qur’an with the same mouth that you have done oral sex with.
As far as it is concerned the wife should not do voluntary fast without the permission of husband because he may have seen some things outside or inside the home and he may have urges to satisfy. But having oral sex doesn't invalid fast until you have taken the filth inside But Allah knows best and all praises are to Allah If you feel guilty then ask for forgiveness of Allah Indeed he will forgive you. Insha Allah.