I get much more than 3 weeks out of them, more like several months before I sand them.

You let them dry out and sand the cut edges good with some sandpaper.
I use plant tie weights to keep them down and rigid tubing, you can be creative there and put them under rocks etc.

Limewood is limewood, brands mean nothing.
Coralife makes the stubby 1.25" version, that's the smallest.
As more use these, I think we will see smaller stones on the market.

Regards,
Tom Barr