Glad you fixed it.
I'm pretty sure the M110 is an interference engine, so you'd need to unbolt the cams to prevent valve contact while rotating the crank with the chain detached.
I did the chain tensioner on the M104, and I finally had success levering the cap on using a screwdriver as a pry bar and then turning with my other hand. It was still a bear and required multiple attempts.

Well, there is the magical 20 degree after position where the valve tension is claimed to be released. I did not scrutinize it but it is possible the valves would all be closed enough at that point to get away with moving the pistons.

How many miles did you have on yours when you performed this task? I just bought one with 164k. It runs quietly for what it is. These engines are a little coarse. But I have heard timing chain noise before on a Nissan. I imagine it is similar.