I understand your fear, sweet heart. I would love to give you more information, but from what you posted I see only some problems which can be just age related, I am not a DR. to know for sure what is written at his MRI report.
Usually many issues we have in our bones are related to age (after age 25 we develop changes in our spine like DDD, stenosis, artrities and so on. Some people more than others). For example my husband had his first spinal MRI at age 40 and he had big bulges, tears and pretty big herniations, canal narrowing and so on. He is 56 now and still problems go on and off, but he is not required surgery for this since same problems may occur over and over.
I had 2 major spinal surgeries and now problems are still there and no garantees that I don't have more surgeries on a way. Since you had one spinal fusion - it opens the door for more especially if you have hardware inserted. Upper and lower levels may collapse due to "domino effect" which happened to me.
Usually most people prescribed PT, mild exsercises, swiming and so on. Only your DR can give you a professional advice what this all is about and how to take care of it.
Best of luck to you , guys.