Doubting a teacher or the path

The canon is unusually permissive about doubt as inquiry: the Kālāmas were told not to accept a teaching on authority, and monks were told how to scrutinize the Buddha himself — by checking what could be seen and heard of his conduct for any sign of corruption. Doubt that paralyzes is a hindrance; doubt that investigates is the path. If a teacher is harming you, no passage asks you to stay.

What the suttas say

don’t go by oral transmission, don’t go by lineage, don’t go by testament, don’t go by canonical authority, don’t rely on logic, don’t rely on inference, don’t go by reasoned train of thought, don’t go by the acceptance of a view after deliberation, don’t go by the appearance of competence, and don’t think “The ascetic is our respected teacher.” But when you know for yourselves:
The Kālāma discourse — the canon's charter for testing teachings.
Where this stops: It is not permission to believe whatever one likes; it ends with what the wise praise. Never a reason to stay with a teacher who is doing harm.
AN 3.65:25.3–25.4 · With the Kālāmas of Kesamutta
Mendicants, a mendicant who is an inquirer, unable to encompass another’s mind, should scrutinize the Realized One for two things—things that can be seen and heard: ‘Can anything corrupt be seen or heard in the Realized One or not?’ Scrutinizing him they find that nothing corrupt can be seen or heard in the Realized One.
The Buddha's own instructions for scrutinizing a teacher, including himself.
Where this stops: Never a reason to stay with a teacher who is doing harm.
MN 47:4.1–4.4 · The Inquirer
Mendicants, these four things can be known in four situations. What four? You can get to know a person’s ethics by living with them. But only after a long time, not casually; only when attentive, not when inattentive; and only by the wise, not the witless. You can get to know a person’s purity by dealing with them. … You can get to know a person’s resilience in times of trouble. … You can get to know a person’s wisdom by discussion. But only after a long time, not casually; only when attentive, not when inattentive; and only by the wise, not the witless.
How a person is actually known — over a long time, with attention, from close up — a standard that applies to a teacher as much as to anyone.
Where this stops: It counsels patience before trusting and before condemning; it is not a reason to stay close to someone already known to be doing harm.
AN 4.192:1.1–1.6 · Facts
For a sensible person who is preserving truth this is not sufficient to come to the categorical conclusion: ‘This is the only truth, anything else is futile.’ “But worthy Gotama, how do you define the preservation of truth?” If a person has faith, they preserve truth by saying, ‘Such is my faith.’
How to hold a view without dishonesty on either side.
MN 95:14.14–15.4 · With Caṅkī

Bring your own situation.