Gas cost is calculated as (23300 * length) + length, possibly to account for a base cost of 21000 and the transfer which is limited to 2300 (21000+2300=23300), but this estimate is just gas units, the estimation should multiply it by the gas price.
Also, the gas cost of transferring the ETH should be covered by the account that originated the transaction, but in the code the gas cost is subtracted from the balance to be distributed. In any case, it should be refunded to the caller.