We run DT hubs on both our road and mountain tandem, and previously sold mountain tandems.

18 teeth is strongest since the tooth depth is deeper.

Never have we had a star ratchet chip like that.

On both bikes, I removed the small O ring that retains the freehub. Two reasons for this.

First is that you need no tools to disassemble the freehub. Simply remove the wheel, remove the QR and everything slides off with the casstte still installed.

Second, on rare occasions off road, the chain has jumped between the largest cassette sprocket and the spokes. With the O ring removed, the assembled cassette / freehub easily slides over to free the stuck chain once the QR or thru axle is released.

I have a small tub of the official DT Molycote grease. While it does work, I find the grease has a short life. Typically I use Mobil 1 automotive gear oil, or in some cases I use a moly fortified Krytox.