You mentioned constant re-pairing with your Xbox controller, but I don't find that to be an issue since the Xbox controller (Elite 2, I think) can retain 2 paired devices. In my case, it was my Xbox and a Galaxy tablet, then my Xbox and a Steam Deck.
If your Xbox controller is a newer version, double-tapping the Bluetooth pairing button on the controller should switch between devices. That should lessen your frustration, I think.
Doesn't meet your other requirements, but since you already have one, maybe it will give you some breathing room until the Steam controller comes out, which will likely hit all your spots.
Happy gaming!
I'd recommend picking up a USB Bluetooth antenna. I had a similar issue with my mobo and finally said "eff it" and fixed my problem externally.
A good bluetooth dongle will likely fix your connectivity issues at a portion of the cost of new controllers and dedicated wireless solutions.