[Edi]

Size 6 is the limit.

Yes, the descriptions are limited. They can be fairly long, though. Just don't write an epic novel.

For the final one, are you modifying an existing unit or creating a new unit? If modifying existing ones, they might have base leadership. Also, check the leadership table in the modding manual against the commander's magic paths. Magic paths grant various kinds of leadership. I am not certain if having #noleader will also nullify leadership from magic paths or if some of the units in the game that cannot lead anything under any circumstances are hardcoded with some flag that makes them behave like that.