The lea ebx,[ebx] is just a NOP operation. Its purpose is to align the beginning of the loop in memory, which will make it faster. As you can see here, the beginning of the loop starts at address 0x00401010, which is divisible by 16, thanks to this instruction.
The CDQ and SUB EAX,EDX operations make sure that the division will round a negative number towards zero - otherwise SAR would round it down, giving incorrect results for negative numbers.
