No sunburn can cause permanent damage to the skin of the sort you describe, certainly not on the part of the skin that didn't burn. Therefore, I don;t think you need to worry that your skin is irreversibly damaged. I really don't know what you mean by saying that your skin, "has absolutely no elasticity or strength." A single sunburn doesn't rob skin of all its elasticity. I frankly think you are over-interpreting minor skin changes because you are afraid that your skin is damaged.
I advise you to use no medications other than what your dermatologist prescribed at the last visit, that you wash with a mild soap and use a bland moisturizer. If there are scabs on your face, do not under any circumstances pick, rub, or closely examine them.
I would be willing to wager that when you see your dermatologist in 5 weeks, you'll be fine.
Best.
Dr. Rockoff