I think you understand it correctly. The proper sentences are (with a little repair work):
ai) I wish we had had this talk before I went to law school.
bi) You are a telepathist. If you hadn’t been who you were this morning, we would all have been dead by now.
ci) I wish I had never built this house.
2b) When the great depression happened, I really wished there had been somebody to help me solve my financial problems.
Back shift-- and other grammatical niceties-- do not always happen in the spoken language: we are often too busy talking and communicating to pay careful attention to our grammar.