The first step is to asses the value of your vehicle in terms of remaining service life and repairs that will be needed soon in addition to the engine.
Is the body in good shape, no visible damage other than a minor door ding or two?
How about the interior, no tears or holes in the seat covers, carpets, vinyl around dash doors etc?
Paint in good shape?
Tires, tread depth, tread wear pattern normal?
Brakes, when was the last brake job?
If all the above are like new or close to it, then get some quotes on your various options.
Option 1: Head restore, new valves, new head gaskets and new timing belt
Option 2: Reman long block.
Option 3: Used engine. I don’t recommend this one but it should be quoted anyway. Find out how many miles on the engine, why it is available and what kind of warranty you will get for both the engine and labor.
You should be able to get 250-300k out of the vehicle. A new Outback would cost $30k+ so if you got a new one and kept it for 300k miles, that would be about $0.10/mile amortized purchase price.
You have maybe 100k left in yours so in theory, you could sink $10k into it and break even on cost/mile with a new vehicle. If a reman cost you $5k, you would break even at 50k miles.
Do you want to keep it that long? Since you broke a timing belt, I’m a little concerned about the rest of the maintenance on the vehicle.