Crank nut went missing and now no start
 

I was out of state for a year and told the wife to have the dealer do the timing belt since we were at 120K on our 2004 XC90 with the 5cyl turbo. Now, 30K later, it loses power for a week according to her, especially on hills. Then just runs terrible and dies all within 10 minutes. I go to check timing and find the nut is GONE! So I get a new one from Volvo so I can turn the engine and verify timing because cranking it doesn't sound hopeful at all. Belt and tensioners all look good. But when I went to align the tops of the cams, I discovered that they are WAY out, apparently. Does this likely spell valve damage before I proceed further?
Numerous codes pointing at camsensors, etc.

i've no experience with it on these cars but on other cars the crank keyway can wear out badly from a loose crank bolt. it will throw off the timing (and timing marks) and reduce power. you would have to take off the crank nut again to see it and maybe the pulley to see if it is worn. also it looks like that pulley (harmnoic balancer) has a layer of rubber, that can come unbonded and the outer part rotates (again messing up timing).