How a print routine usually works is that it adds $40 (the size of 2 tilemap rows on the GB) to the tile address after each line.
You could single-space it by changing to $20.
You'd have to disassemble the print routine.
If you can understand ASM, it's probably simple. If you don't, it's a lot of work.
Start be using breakpoints to set a read breakpoint on $57C5 (your text address after being converted to a CPU address)
It probably does some cp instructions to check if the value is a newline character.
(like if a newline was FE, the following instructions "cp a,FE jr z,xxxx" would mean the linebreak routine was at xxxx)
On the Game Boy, RAM $8000-9FFF is VRAM. You usually want to avoid directly messing with that, and only do stuff with the CPU RAM ($C000-DFFF)