Assembler 16 BIT DOS keyboard input output on screen error

Question

I have following code Basically Im trying output string on middle of console window, string is inputed from keyboard

.MODEL small
.STACK 200h
.DATA
Buffer DB 81, ? , 81 dup (?)
.CODE
Start: mov AH,0Ah
mov DX, offset Buffer
int 21h
mov AH, 0Fh
int 10h
mov AH,0
int 10h
mov AX,80
sub AL, Buffer[1]
mov BL,2 
div BL
mov BH,0
mov DH,12
mov DL,AL
mov AH,2
int 10h
mov BL, Buffer[1]
mov BH,0
mov Buffer[BX+2],'$'
mov ah,9
int 21h
mov ah, 0
 int 16h
 mov ah, 4Ch
 int 21h
END Start

and my output in DosBox is very strange

can someone explain what I'm doing wrong?