Till they... Tenses

[barnej0096]

When Rich (tell) his parents that he and the girl he (date) for a couple of months (get) married, his mother (try) (persuade) him (wait) till they (graduate). But later she (admit) if he (listen) to her he (be) wrong.
I think it should be: told, had been dating, were getting, tried to persuade, to wait. But I don't know what tense I should use after till, past perfect or present simple? Is it the 3rd conditional in the last sentence? 'But later she admitted if he had listened to her he would have been wrong.

[bhaisahab]

When Rich (tell) his parents that he and the girl he (date) for a couple of months (get) married, his mother (try) (persuade) him (wait) till they (graduate). But later she (admit) if he (listen) to her he (be) wrong.
I think it should be: told, had been dating, were getting, tried to persuade, to wait. But I don't know what tense I should use after till, past perfect or present simple? Is it the 3rd conditional in the last sentence? 'But later she admitted if he had listened to her he would have been wrong.

I would use "had graduated". This is correct, "But later she admitted if he had listened to her he would have been wrong."