Looking good.
The
FW jetpack is nice, but I think you need to use a lot of bitz to make it. How about replacing the drone bit fins with plasticard?
I prefer Milliput to Green Stuff for bulk filling. It's cheaper, and sets quicker to a harder finish which can be sanded, carved and drilled. It can easily be shaped with wet tools while soft.
Personally I use two different Milliputs (medium and fine), Green Stuff and Brown stuff, depending on the application.
The best kind of saw for the cuts you want to make is a jeweller's saw or coping saw. It looks like this;
The thin blade can go round corners. It often snaps, so you buy spares in packs of one gross and just put a new one on. This means the blade is always sharp. The kerf is minimal.
The standard
GW style back saw is good for straight cutting.