The ideas given here in the post are all good ideas but you need to give them more than just one or 2 tries in 3 days.
Patience... be kind to yourself. You want to prove yourself overnight but the greatest achievements may have taken 1001 nights. You've spent a considerable amount of time on it so it must be hard to give up... perhaps like the greatest classical guitarist you need to find the right mentor.
On the whole I think you are taking the right course of action for you. Not everything comes easy and you would know yourself best. Perhaps right now it is a good idea for you to shelve the idea of being able to photoread, because perhaps, as you say, there are other priorities in your life right now.
You said yourself that your problem is "performance anxiety" related, well I don't think that learning to photoread is going to help you overcome that. You've got too much at stake and since you are in training to become a Operatic Tenor you must be working with professionals that can help you overcome this anxiety. Once you've learnt the skills there you'll be able to come back to Photoreading if you so desire. 
LSC have a paraliminal tape called Anxiety Free, the Self-Esteem Supercharger and the deep relaxation tape are good also. You have to make up your mind that they will work... if your mind is made up they won't then they won't.
Cause "Whether you think you can or think you can't,- you are right."
Yes, let yourself of the hook. You must be true to yourself. You are not the first to have shelved the course and there are others who have have come back later to succeed.
You've identified the problem yourself and we have given you a number of suggestions that can empower you to overcome this problem. Relisticly though we know that anxiety does not disappear overnight. Be patient with yourself, detach and ask yourself is your anxiety really warrented?
Honour thyself,
Alex 
