Bishop Schneider: In his activities, he should have perhaps an older or more mature priest to whom he can give an account of what he is doing, or discreetly seek guidance from a retired, good Catholic bishop. This would allow him to propose his actions and receive accountability. This is only a temporary measure, until Rome once again has strong leadership that unambiguously defends the Catholic faith, which will undoubtedly come.
These situations are for emergencies. Alternatively, he could seek a religious community with a superior who still upholds the traditional Latin Mass and the true Catholic faith. There are several possible approaches, but the main point is that he must not act as his own Pope or bishop. He must have the humility to submit to the oversight of another good priest or a retired bishop.