I won't give a specific solution.
What works for you ultimately depends on you; be it intermittent fasting, OMAD, cutting sugar and/or salt, simply eating less, working out, a combination of the previously mentioned, etc. but what I feel allowed me to actually lose weight (~50 pounds so far) was accepting that -- whatever you end up doing -- it's not temporary. It's a lifestyle change. You're just going to regain that weight if you return to the habits that brought you there in the first place.
Mentally, I also approached it as "one step at a time". Weight fluctuates for all sorts of reasons be it water intake, you just ate, etc. I didn't get discouraged as I saw the number go up and down a few pounds here and there, but continued to view every few pounds as a milestone worth celebrating (not with a cheat day, mind you). The general trend kept going down, I was getting and remaining healthy, and that's all I really cared about.
That's a solid argument toward using an AVP vs a traditional PCVR set up.
... So why not just do that for a fraction of the price on the Quest 3? I do everything you listed on mine, I even take it with me when I travel without any perceived constraints. I, too, can use Steam Link (although I prefer Virtual Remote Desktop currently) and even found myself making some use of the new Xbox GamePass app, and yes, it also pairs with my controller, and my Logitech keyboard and mouse too.
I understand the AVP can fill a wider role than a standard PCVR gaming rig set up, but I feel what you describe as something to compare with the AVP is honestly kind of outdated.