i would not bring another male into the mix, not in a million years!! sorry for being blunt
and i would suggest getting at least another couple of girls on top making a ratio of 5 to one as drakes are very sexual creatures and can potentially over do it with the females, who can in extreme circumstances die
i have 3 females and one male currently running together, and a separate pen housing two drakes, they were running all together all 3, but fights started happening more and more often and had i not made the decision to separate i would have lost all 3 males. (i have a ratio of three female to one male and i recommended more - i am getting more this spring, but i had a failed hatch last year hence my numbers are down)