I did some thing similar last yr with the emergency blankets. It worked very well..but I had taped it to a set of plastic shelves. It seems that you are loosing light with it draped. Move the light to be mounted under that shelf I see and surround that with the blankets. I am in MA. I grew toms cukes,basil,cilantro,delphis,larkspur,rubickeas ect this way last year. This year I am doing mostly the same thing..but I am suing the auto sun shades in place of the blankets on 3 sides and the blanket on the front. Here is a link that might be useful: plant condo. use the next button to see more.

19½" doesn't sound like nearly enough room. Imagine carrying a large, heavy box and wanting to put it on a shelf. The box would be against the body, as it should be for heavy objects, and you'd need to take into account the thickness of the average body and enough room to pivot to place the box on the shelf. Something like 30"-36" would be far more manageable and safer. As for the distance between the shelving and boiler, you should check with the manufacturer and/or consult local code, especially if this is a commercial building or something like an apartment. Otherwise, I'd think a minimum of 36".

Houzzers usually opt for a credenza under the TV rather than a unit that surrounds it. Lighting a few display shelves might help lighten the visual heft of the piece, as would glass.

I strongly recommend you do not remove the backboard! it might actually mess up the structural integrity (as in, it could get all wobbly). or attempting to remove it might break the piece. I honestly don't think removing it will make this look better in any way. however, you might look into whether you could carefully remove the glass, which makes it look like a dining cabinet. store it away carefully in case you ever want to put it back. this would look great if the paint was stripped and the wood refinished. be very careful-- it might be a veneer! you really don't want to sand through that. at first I thought it should have never been painted, but maybe it was originally that way. black paint looks great in the inspo pics. in that case I'd choose a softer matte black. pieces like these were mostly meant to be for displaying fancy dishes. alternately, my sister used a vintage sideboard like that as storage in her kitchen. here's some inspo for how you could style it for a living room. keep it sparse. I like how they added a record player. your sideboard looks like it it might be the right size to store records in the bottom shelf!