Hi Tom,
The five ways you've written to make the nouns plural are correct, but there is also a simple rule and that is using only "ان" and "ها" . It almost works for all the nouns. Some of the linguists believe this is more Persian and this way is preferred to use Arabic plural signs. Though it's good to know Arabic forms too, because they are still used in Persian and they help you to understand some of Persian texts easier, but you really don't need to use them.
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About using ها or ان, I would say ها is much more widely used. You can use it both for living and non living, just like the examples you've mentioned. There are some exceptions though, like آقایان which you said. But it's not like آقاها is wrong, it just doesn't sound that natural. I don't think there is a rule to find out these exceptions, because they aren't really that many.
You just need to get familiar with them over time.
But the the number of exceptions in making plural with ان is much more. In spite of ها you can't make many of the nouns plural with ان, specially in colloquial Persian. I mean it is more used in poetry and literature. I try to write some general rules here:
1.You can make most of the livings plural with ان:
مردان، زنان، مرغان، اسبان،
though there are exceptions again. خانمان or انسانان don't sound correct for example.
2.Most of the plants, like:
درختان، نهالان، علفزاران،
but still nouns like چمنان، گلان don't sound correct.
3.Most of the body organs like:
چشمان، دستان، انگشتان، لبان، but again گوشان or پایان for example, are wrong.
4.Most of the nouns related to time like :
روزگاران، سالان، ماهان، شبان، روزان
Overall I'd recommend you to use ها more. It's easier and more common.