Came on to see your planned Retro-fit.
A Color suggestion....don't go with a Black Ceiling. I suggest instead a very Dark Neutral Grey (see example) done in a high quality paint (that is still reasonably priced) such a PPG Diamond Base 3.
(The above is a Custom color made to be dead-on Neutral (...if you print the image out Home Depot can Scan the tag...)
A Black Ceiling is strictly "functional" and not attractive, and your Theater is more design-oriented, with a cosmetic appeal that a Black Ceiling would seriously impact with the lights up.
Black Paint must be "super saturated" and applied very carefully....spraying is best. And with that light existing Ceiling, it's best to do such a Black Ceiling in stages, first applying a Medium Dark Grey Base in a basic Flat Paint so that coverage by the Black does not have to do it all.
The same applies to the very Dark Neutral Grey.....but the Grey won't look either dismally dull, nor will it be as expensive to do. Black is "Old School" reasoning....a thought held by many mostly because it would seem the obvious choice. But unless it's done correctly using some pretty pricey Paint (...and lots of it....) with a high Acrylic content, it usually shows a patchy, uneven look,....often looks dusty, and way too often...if Rolled on...shows every Roller mark or unevenly applied area that was left by anything less than a perfect job.
When I overview the room, I see a Very Dark Grey Ceiling that extends the same color around the shallow Fur out and down each of the Faux Columns, stopping at the Wainscot Chair rail. The inset areas could remain painted with the mid-tone Neutral Grey,preventing the turning of the room into a Tomb. Dark Grey would highly compliment the Deep Red Draperies, while still allowing the Seating to be a darker focal point.
I am / have always been all about cosmetic appeal, and save the use of Plush Black Velvet, I've never seen Black as being anything but a detriment visually. I've done quite a few Theaters in a Red-Grey motif and they always elicit appreciative comments.