What is the ruling on saying "Ya Allah" during a sudden fit of anger? And what is the ruling on taking a job through wāsiṭah (favoritism/mediation), and how can one repent and absolve themselves from its earnings?

There is no harm in saying "Ya Allah" (O Allah) when angry if the speaker is seeking Allah's help, or His aid, or supplicating against an oppressor. Seeking Allah's aid and help is permissible and desirable, as stated in the Almighty's قول (statement): "When you sought help from your Lord, and He answered you." The pronunciation of "Ya Allah" with the extended 'alif' of 'ya' was well-known among Arabs. It is recommended for an angry person to perform ablution, seek refuge in Allah from Satan, and change the position he is in. Supplicating against an oppressor is permissible, but forgiveness is better.