Wonderful space!! So its a separate "building" from the house it looks like? Can you provide details on the split AC unit?
You've done your homework on the construction and room acoustics, well done - the room is prob the most significant "piece" in this hobby, one which I personally am very much into (acoustics). One thing I will mention FWIW on the acoustic side, some QRD type of diffusion on your entire front wall would be something to explore if you ever have the itch. GIK gridfusiors are inexpensive (comparatively speaking) and work really well. Also covering the TV or better yet throw two or three 244 broadband in front. Anyway, great job.
I love the yard too! Mowing close to ..8 acre and all shrubs, irregation etc.. is getting old for me. You have my dream yard, rocks, lol!!