Just reread where you said your room is 18 x 24 feet. It sounds like our family room, which is 32 ft long. Too bad yours isn't just a tad longer, too. Of course, at the end of my family room is the door that leads to his den, lol. Where he seldom goes. Too bad I can't send you some of this house.
How about inviting in a couple of friends and moving him down to the far end and plugging in the tv down there? Give yourself 18 x 18, and put up a nice track across the ceiling that holds one of those folding doors. Let him have the other end of the room. Heck, how much room does a chair and a tv require? THen arrange your studio to suit yourself. And close the track riding door. If you miss him, no problem opening it.
If you want to put up a regular wall, bring in a handy man. Make it a HUNKY HANDI-MAN, and hubby might get the idea to turn the tv off once in a while, lol. THey don't usually charge more just because they are good looking, lol.
I have my computers, two sewing machines, three chests, a tv entertainment center (nothing like your dh's), two couches, four dogs, a formal dining table aka sewing table, lol, and moved my dh's rolltop desk into this room, and we get along. Hey, if I get tired of him, I turn the tv to something he doesn't like and he goes away. I don't do sports. We have a living room with tv, bedrooms with tvs...den with tv. Is that all it would take to get your to move along?
Think about it. That's a big room. lol...I should know, I hang out in one that size.