On a symbolic note, Pound claims here that usura stops young men from asking young women out on dates, and keeps new love from blossoming. On a more literal note, though, young people might not have as much time to meet new people and date because they're too busy trying to make enough money for a good house and a car. In any case, Pound is basically saying here that usura corrupts relationships between people and stops real love from growing.
It has brought palsey to bed (45)
Hey, not only does Pound say usura is lousy. He also says that making your money off of other money instead of producing something real is actually the same thing as being paralyzed in bed, or to put it more bluntly, being sexually impotent. Just a little something to think about for all the businessmen who think they're "real men" because they're rich and have nice cars.
[…] it lyeth
between the young bride and her bridegroom" (46)
In case we didn't get his point loud and clear, Pound helps close Canto XLV by yelling that usura is against nature in all caps and in Latin. He's definitely trying to give us a sense of how beautiful human nature can be, and of how brutally our obsession with money can warp our true nature.
They have brought whores for Eleusis (48)
For starters, Eleusis was the name of a town in Ancient Greece where people got together and celebrated fertility—or in other words, people's ability to sexually reproduce. But instead of fertility being a beautiful and sacred thing, Pound suggests here that people who practice usura end up bringing dishonor to the most sacred aspects of our lives. It's a shame that Pound chooses to symbolize dishonor with the image of prostitutes, but that's basically the point he's trying to make here.