Yo Garfield,

i can only confirm that you can save as much projects as your SD card can hold (there is already a SD card included and I think you wont be able to fill it up with songs...).

I can't tell, what's the maximum number of steps per project, but I assume that your calculations are right, especially with 384 steps per sequence.
I think that's a lot since you can arrange your sequences in presets and presets in scenes. Inside these sequences can also be arranged as playlists. Have a look into the manual on page 15.

Hope this helps :),
Best,
jingo