Is the husband's saying to his wife, "This is not too late, you can go and marry with them," considered a third divorce, knowing that he had divorced her twice previously?

This phrase is a euphemism for divorce, not an explicit one. If you intended divorce by it, then it has occurred, and your wife has become irrevocably divorced from you (Baynunah Kubra). If you did not intend it, then it has not occurred. Mere contemplation of divorce, without actually enacting it, holds no weight. This ruling applies between you and Allah because you uttered it in a state of anger and dispute. Therefore, if you did not intend divorce, or if you intended something else by the euphemism, then you are truthful in what is between you and Allah.