The clam is not dead. When they die, it happens very fast and there is little doubt when you see it.
Clams can be difficult at first and they can take 1-2 weeks before fully opening in my experience. I'd go with the direct feedings and pick a spot to place it and stick with it. They don't like being moved so much. I've never noticed a maxima clam complaining about the substrate (i.e., sand vs. rock).
Also, I don't know what the verdict is on clams and T5's, so I 'll leave that to someone else to address. I've read MH only for maxima's but when I was reading up T5's were kind of new (and I didn't have them so didn't care!).
Many people have had good luck with FW dips to address pinching but I would give the calm some time to acclimate to your system first before I tried that. You will find many others completely opposed teh FW dips and say they accomplish nothing. Good luck sorting that arguement out. I say if it is pinching anyway it is going to die, so what do you have to loose?
Dale