Is it obligatory to pay teachers if the questioner suspects they have not been paid, and is this suspicion considered a form of scrupulousness (waswasah)? And is it obligatory to seek forgiveness from friends who have been wronged, or is that considered a form of scrupulousness (waswasah)?

You must pay the tuition fees to their owners or seek their forgiveness if you are certain they were not paid. Do not pay attention to doubt, for the original state is the acquittal of responsibility. If you have wronged people and can ask for their forgiveness without embarrassment or harm, then do so. Otherwise, sincere repentance between you and Allah is sufficient. You must turn away from all whisperings (waswas) and not pay attention to them. Seek Allah's help and occupy your time with what benefits you.