I'm not surprised you are having clearance issues with the rear tires.
My Dad had a similar vintage Outback and in stock trim there simply wasn't enough clearance to mount tire chains in the back. This would normally not be a huge issue except that this was his first automatic car ever (thanks to his 2nd wife's insistence) and when descending his horrible mountain road on glare ice the rear unchained tires would lock, the ABS would cycle the brake pressure back, and the car would rocket down the road out of control up to something like 15 MPH when there would be enough engine braking provided through the auto to slow it down. When the road was bad enough that chains were required 15-20 was WAYYYYYYY to fast.
After this happened to him twice (both times he avoided damage to the car or himself- but not his underwear) he and I kluged up a defeat switch to shut off the ABS and were able to source spacers to move the rear wheels out about 3/4". The spacers allowed the use of Whitestar style inner loop chains but they would still rub at higher wheel speeds, so Dad mostly relied on shutting off the ABS and using only chains on the front- fine for up-hills but a little sketchy going down.