How about using the exhaust gas heat directed through some PVC pipe? Or let down the tire pressure to make the ice take the weight of the car?
Hardware stores have a “de-ice” material (grains of a bio-degradable) that does not rust like salt.
Salt won’t do much on thick ice, at least not in less a day or two and repeated applications.
I’d suggest just lowering the tire pressure (assuming access to the valve) and the flex of the tire would put of the weight of the car on the ice.
Drilling a hole towards the valve and filling it with hot (not boiling) water would work.
If you have some appropriate pipe (PVC or “dryer duct” etc.) you can direct the vehicles exhaust gases to point at the wheel. Pack snow around the wheel to create a “cave” to trap the warm air.
I’ve had the same problem with a snowmobile covered in an ice block when it was parked under a deck – snow thawed and dripped through and froze again on the snowmobile.
We half-filled small garbage bags with warm water to create a “compress” for the top of the sled. It took two days of warm water and de-icing to get the sled thawed out. The final step was to start the engine (once ice was out of the intake air box) and its own cooling system is a heat-exchanger on the rear of the frame. The lower inside of the engine cover was full of ice that took another half a day of riding and sitting to melt away before the front suspension would move freely.
This was pre-YouTube … it would have made a fun time-lapse video.