The soil under the shells should be incredible! Nothing prepares soil like mulch. Whatever you do, do NOT rototill that area prior to installing the lawn.

Keep in mind that when vinegar is used as a herbicide, the contentration is fairly high, and you're supposed to use it when the sun is out. Many things that are fine or even good for plants are toxic at high conentrations. I've given a fair amount of vinegar to shaded weeds, and they were fine (they didn't even flinch). I imagine a little calcium acetate on the plant isn't going to hurt it. Fertilizer foliar sprays generally aren't done when the sun is out, and the concentration is very low. So, you're unlikely to kill the plant, unless you use the wrong ratio of fertilizer to water and/or apply it in the sun.

That is tortoise shell grained wood veneer. They did do furniture with tortoise shell inlay and I suppose in VERY expensive, sultan;s palace types of furniture, they did use av eneer of tortoiseshell....but the term tortiose shell veneer means a wood grain looking like tortoise shell....usually a burl grain. Another big clue is the fact that your piece is manufactured....very unlikely to have any exotic materials.

can I see the inside of the socket. and what is the exposed thread and nut from the first picture?