Oil in coolant is the main problem. It could just be a head gasket. But how long has it been like that? Need a leak down test of the cylinders to pinpoint where a leak may be. It sounds like the oil caused damage to parts that don’t like oil. As long as there is no coolant in the engine oil, it might not be too bad. Hmmmm, a Subaru is actually something I haven’t really worked on. Just changed oil on. I did a quick search and found 8 engines for $1,300 each in New Jersey. Plus shipping. I’m not sure how much the shipping would be.
The cheap tensioner should be fine. I’ve been through 3 cheap timing chains. The timing kit for my car, that is OE, is $345. But the other day, I just noticed they have just the OE chain for like $69 or something like that. I’m going to have to order that and change it one day.