Congratulations on reaching this step in the develpment of your tank!
It's so interesting to get live rock and watch all it become covered with interesting things. As you say, there's already much to see. You'll still be finding new algaes, featherdusters, amphipods and whatever 6 months from now. Be sure to buy a good magnifying glass so you can view everything close up!
I see the many little octopus dens and passages that you've left in the rock. You were right to test the stability carefully. The only casulty from falling rock reported on Ceph Care was years ago when a small octopus hung onto the rock with a few arms and the feeding stick with others, pulling a rock down on himself. Your rock should be fine.
I assume you have a sump under the tank.
And Tony, that's an aquarium stand, they're usually heavy wood and/or very strong plastic, so it should be fine for the tank, but no doubt Ryan has looked into that.