That's some pretty darn cool deductions you got there. I like them.
I especially like where you put the hydrogen collectors. I think that makes much more sense than in the nacelles, like TNG. I've downloaded the image to my machine and will use it as reference if I ever need to. Damn fine work.
I just from this
site that slush hydrogen is approximately "0.1967 gram per cubic centimetre".
This is equivalent to 196.7 kg/kL, which is the units I used in the above table, in which I calculated for 165.6 kg/kL at 20K: liquid, not slush.
The thing that gets me, though, is that when I went looking for data before (about two years ago, so I forgot where I got the data) I found that it was 152 kg/kL as a solid, less than what I was quoting as a liquid.
Thus my earlier "deuterium is less dense as a solid" comment earlier.
At the same time, I've encounter the 196.7 kg/kL data point recently but I didn't give it much credence.
I also want to state that my statements about rocket propulsion is a bit glib. Exhaust velocity does not effect rocket velocity linearly. The effects are also logarithmic. But describing the difference in the curves is not easy for me to describe. As such, sometimes it's better to have a better exhaust velocity than it is to have a high mass ratio. It just depends.