I haven't tried Fusion 360 yet, so I can't compare. For lack of any other options I would definitely use FreeCAD again. It wasn't a horrible experience.
I love supporting open source. For example, the 3D printer I have is the Lulzbot Mini 2. The company behind it is ... aggressively open source, to put it mildly (_everything_ is open source. Even their manuals for factory assembly are online.). Which is why I went with FreeCAD initially. But I lost a lot of time to A) the awkward UI; and B) bugs. Having just now, the day before Christmas, finished wrapping the gift ... I wonder how much time I would have saved using a "professional" CAD solution. shrug
Words of advice if you do go down the FreeCAD route; learn about dataplanes and shapebinder (check YouTube for tutorial videos). They are somewhat recent features. If you just look up FreeCAD tutorials you'll find a lot that tell you to bind sketches to faces. That's the old way of doing it and it can lead to a lot of problems. Dataplanes are the new way of doing it.
And be careful in the sketcher. A number of times I've had it tell me a sketch is fully constrained, but I was scratching my head because I didn't think it was fully constrained. A day later I'll go back into that sketch and it'll have realized its mistake and moved the sketch around (had one failed print because of that bug).
> Don't have any source code available?
I'm thinking of writing a blog post about the whole project at some point, with all the documentation and such. Bit exhausted right now...
Best of luck with your 3D printing!