Firstly, it's not blood, it is myoglobin. Blood flows through veins and arteries. Myoglobin is present in the muscle. Anyway, it's a little beside the point.
Now, to your steak. The 1/4 cup of moisture loss from a frozen steak cooked at this temp is not surprising. Moisture loss increases with increase in temperature. Also, freezing ruptures the cellular walls and so the freeze thaw process increases the moisture loss. Have you ever noticed the mixture that pools on the plate upon which you thaw a steak? This is myoglobin from the traumatized muscle.
I'd consixer dropping the temperature to 63.5C. This is at the lower end of the medium well range, but even that little change will have an impact on the moisture loss.
Another thing to consider is the thickness of your steak. Half an inch is very thin on terms of sous vide processing. It is fine for the cooking it in the water bath, but it is very easy to over cook it and tighten the muscle further when wearing it. Remember, that steak is already cooked to your required doneness. The seating is for presentation and flavour. In order to get the desired surface treatment on a thin steak without pushing the interior beyond your perfection you need to be very very quick and that takes experience.