I'm very impressed with the accuracy of that crossbow. I've shot archery all my life and knew that crossbows were more 'snappy' than normal bows, but damn.
Regarding ballistics, you can use a standard ballistics program like you use for bullets. The Berger program:
is a good, simple program to use for this. You will have to know the weight of the entire arrow (I thought they were called 'bolts'?) in grains. For caliber, use the diameter of the shaft, in inches. Ultimately, you will have to determine BC by trial and error based on your drop data, but a good place to start is to enter a G1 BC that results in a form factor of around 1.1 or 1.2. That should be close.
If you can set up two chronographs and measure the velocity at two distances, then you can derive a BC that way. Once you have the BC of the arrows/bolts, everything else about the program works the same way.
Note that if the crossbow gets out of 'tune' at all, resulting in the arrows flying with any amount of yaw, that the BC will be degraded quite a bit. You mentioned a 'paper test' in your first post, which I assume has something to do with tuning the pitch/yaw out of the crossbow. It would be a good idea to check once in a while to make sure it stays in tune, or else your ballistics will degrade significantly.
I also think it's a good idea to do some serious verification shooting with whatever broadhead you plan to work with. Even if you have to destroy a couple heads to get the drop fully verified, it's probably worth it to know how the arrows will fly 'when it counts'.
Out of curiosity, how much does something like that cost? Looks like a bunch of fun! I wonder what the max effective range is, based on hitting an 8" vital zone with lethal energy? My guess would be up to 300 yards? You'd need a lot of elevation in the scope!