Grammar books vary vastly in guidance on Modal verbs and the Conditional or Unreal Past. We can exercise our grammar relativity, to manage.
We can use Form Relativity with the Progressive and real verbs. We can use stories. “I’d be reading horoscopes”, says Ms. Seges. “That is …?” (Mr. Seges does not believe Ms. Seges would ever read horoscopes.) “This looks like a calligraphic copy of Vespucci’s letters. It was slipping out of our backyard hedge, no covers or front matter.” “Hadn’t it sure taken a lot to make such a book, I’d suspect that Babbitt next door. Bill once wrote me the book I was looking for was as likely to be obtained as a calligraphic of Vespucci’s originals. It was completely a legend, he checked with the Freeman’s.”
We do not have to view Modal, Conditional, or Unreal Past patterns as separate. With Perfect tenses, our syntactic HAVE helps tell about real time. It has an open real-time frame. With the Unreal Past or Conditional, HAVE tells about hypothetical time. HAVE is not part the real map, then. It comes with an auxiliary compass for relative time.
We can view verb forms as generally relative, for hypotheses. PRESENT forms can tell about the FUTURE. PAST forms can tell about the PRESENT. ANTECEDENT PAST forms can tell about the PAST.