certain staffs not allowing dynamic volume adjustment

I'm guessing this was imported from MIDI, as it has the same sort of oddly notated rhythms typical of non-quanitized live performance. As such, you should always consider resetting the MIDI velocity so the notes will respond to dynamics - Ctrl+A to select all, Notes in the Inspector to limit selection to just notes, then reset the velocity fields in the Inspector. But, "velocity" is not meaningful for instruments that respond to single note dynamics. Not sure what you mean about the alto sax not resetting in the inspector - it does for me - but because the default alto sax sound in the default soundfont use single note dynamics rather than velocity to control volume, it's not going to matter much. If you prefer setting velocities note by note and don't need crescendos and diminuendo or other dynamics changes to work on single notes, change from Alto Sax Expr to Alto Sax in the Mixer, but be sure tha'ts really want you want to sign yourself up for. Normally it will be much better to simply reset the velocities and let the dynamics you add to your score do their thing normally.