In BOOTLOAD.ASM - Directly after you have set up video mode 3, the cursor will be in the upper left corner. You don't have to explicitly put it there. Moreover the function that sets the cursor uses the BH register to represent the display page for which you want to set the cursor position. You omitted this value and thus it's possible that BIOS used a page different from what you need which is the 0 display page.
In BOOTLOAD.ASM - Directly after you have set up video mode 3, the cursor will be in the upper left corner. You don't have to explicitly put it there. Moreover the function that sets the cursor uses the BH register to represent the display page for which you want to set the cursor position. You omitted this value and thus it's possible that BIOS used a page different from what you need which is the 0 display page.