A rough pronunciation:
- I read a book - Léim leabhar (laym lah-wur)
- I read books - Léim leabhair (laym lah-wir)
If you are finding it hard to pronounce that "ir" sound you can use an adjective e.g. Léim leabhar amháin (I read one book), Léim cúpla leabhar (I read a few books) or Tá mé ag léamh a lán leabhar (I am reading a lot of books), note that the singular is used here because "cúpla" and "a lán" make it clear the noun is plural.
They should, but the people here don't show the difference between the two for some reason. :/ I hope they fix this..... By the context of a sentence though, you can usually tell whether a word is plural or not. If it's not obvious which form is being used (plural or singular) I don't really know what can be done.
Broad r - sounds like an American r Slender r - a vibrated r on the roof of your mouth. That's about as basic as I can get. But it's different in different regions of Ireland, too. Some people pronounce both slender and broad r as the same sound or sometimes one is trilled and the other glottal stopped.