I think it's a nice change of pace to have someone with genre-busting abilities not also be an economic/political genius (beyond the "I got tricked once and now I'll never be taken advantage of again!" freebie they usually get). Either that or he knows he's being taken advantage of and has...
The jealousy trope is annoying because the point of this manga isn't the romance, it's the rockets. Where are the rockets? I was promised multi-stage liquid-propellant mach-2-exceeding space-reaching goodness.
What a classic ending for manga of this genre - the last joke is on the reader who expected anything different after 200 chapters. I'm not even disappointed, this is a manga that is true to its premise to the end.
Regarding the end note: that font style is incredibly common for jazz/pop arrangements, where it's meant to look like a classic (for the genre) handwritten score (often to the detriment of readability). The Real Book is probably the most prominent example of its (or at least a similar font...