^^^ = Longest sentence ever.
I wouldnt recommend forcing your snowflake to dig through the substrate. Get yourself a masonry drill, and some zip ties. I just did this this past weekend, drilled my rock, ziptied it all together. It allowed me to make some pretty crazy formations, and keep the rock stable.
I would also recommend buying a piece of PVC large enough for him to live in as a full grown eel. Then cover this with live rock. It will create a large, safe, stable place for him to hide. No worries about a potential live rock collapse killing your fish.
Good luck!