I only took a quick look at your code, but it looks like you missed some of the I2S1 references:
REG_WRITE(I2S_INT_CLR_REG(1), (REG_READ(I2S_INT_RAW_REG(1)) & 0xffffffc0) | 0x3f);
I’m pretty sure that’s accessing I2S1 registers there. I saw a few more lines like this. Sorry it’s not easy to change I2S peripherals, that’s something Sprite_TM’s example code didn’t handle well, and I didn’t bother improving as I figured there would always be two peripherals so why bother.