The book Training For Climbing by Eric j Horst has some good exercises for curing/preventing muscle imbalances. You can get it from amazon.co.uk and is well worth a read. Get well soon!
good test. If you lay flat on the floor, face down with your arms bent at a right angle above your head (your upper arm runs past your ear and your lower arm should be at a right angle in front of your head) you should be able to keep both your elbow and shoulder on the floor and still be able to lift your forearm off the floor! If you find this difficult then you are going to have problems eventually.