Ford Focus 1.5 Duratorq timing belt noise + broken tensioner

Hello,

My Ford Focus 1.5 diesel started making some horrible noises and running rough (but no service now signal).

Fast forward the next day I felt sudden lost of power, noise intensified and the "Engine Service Now" message popped up.
I was just around the corner from my mechanic and I left the car for diagnosing. My mechanic called to let me know that he needs to investigate further and that worst case scenario the engine is finished.

We found out later that one of the tensioners broke (correct me here if that's not the right part shown in the image) and the belt skipped three teeth and did some damage around.
He believed that the engine is fine and that I can get away by replacing the belt and the damaged parts - he did replace everything and the next day I went to pick up the car.

He warned me that if the engine light comes on I should bring it back so that we can read the error code, and as told It showed up a minute later.

I brought the car in again and the error code was related to air intake. The car is running smooth but there is no power because of the limp mode. I can also hear unburned diesel smell inside the cabin but exhaust seems fine.
He told me to bring it again so that he can look at the whole air intake system. He suspects that in these cases the most common issue is bent valves (as does my research).

If that's the case isn't that something that he should have looked up before we changed parts? If bent valves are the issue should I continue putting money into this issue or find a new engine.

Also, is this a common issue for this type of engine, I have yet to find the same issue mentioned in the forums and also the mechanic said that this is not typical.