Coming from a jewish background (Judaism also "bans interest/usury"), I advise you to take these rules with a grain of salt. In the case of Judaism, there were (sometimes still are) many tricks to the system, for example: you could lend with interest to non-jews, you could have and trade slaves, etc.
I'd assume Islam, being similar to Judaism, uses the same kind of tricks. For example, after a quick search, I found this:
"The common view of riba (usury) among classical jurists of Islamic law and economics during the Islamic
Golden Age was that it is only riba and therefore unlawful to apply interest to money exnatura sua—
exclusively gold and silver currencies—but that it is not riba and is therefore acceptable to apply interest to
fiat money—currencies made up of other materials such as paper or base metals—to an extent."
Thank you for chiming in. I'm aware that Judaism bans interest, but you're also correct that thier Rabbis made loopholes such that only Jews don't lend money with interest to other Jews, but they're allowed to lend money with interest to non-Jews. Christianity bans it as well, but people don't practice what they preach so to speak.
With Islam, there are no such tricks, because it explicitly calls out tricks like what you're mentioning and warns people who engage in them. Of course, it doesn't prevent some people from claiming certain things, but you'd have to look at the overall consensus. If you ask scholars today, they will tell you that you cannot deal with interest with fiat money, the consensus is that you cannot take an interest-based loan or mortgage from a bank.
I can't find the author of the book you cited, but it seems he's misguided and conflating two things. There was no paper money back during the Islamic Golden Age, so I'm not sure why he mentions it. Secondly, he seems to be conflating Riba that applies to certain materials (explicitly mentioned in [0][1]) with Riba due to loans. The Islamic notion of Riba encomposses more than simply usury and interest. For example, exchanging 5gm of 22 karat gold for 8gm of 18 karat gold falls under Riba, and is prohibited.
What is permissible is to have exchanges of different types, as mentioned in those Hadiths. For a modern manifestation of this: I can exchange a certain amount of USD to a different amount of Euros. However, I cannot lend out $100 and ask them to be returned $105.
Yes, and if you look up the opinion of present-day scholars, you'll find that many of them call said banks out on it (if it walks like a duck and quacks like a duck). While I'm not a scholar, I completely agree that it's jumping around the issue and it is almost certainly interest. It doesn't mean Islam allows it. This in my opinion, is a manifestation of what I mentioned how the West pushed their usurious banking system onto Islamic nations, and because many of those governments were installed by Western nations, now the people are having a difficult time breaking out of it.
I'd assume Islam, being similar to Judaism, uses the same kind of tricks. For example, after a quick search, I found this:
"The common view of riba (usury) among classical jurists of Islamic law and economics during the Islamic Golden Age was that it is only riba and therefore unlawful to apply interest to money exnatura sua— exclusively gold and silver currencies—but that it is not riba and is therefore acceptable to apply interest to fiat money—currencies made up of other materials such as paper or base metals—to an extent."
Source: https://books.google.cl/books?id=1MKrCQAAQBAJ&pg=PA23&lpg=PA...