Whoa whoa whoa... Is he eating if so then why do you want to put him down because of corkscrewing? Stress and excitement causes corkscrewing in spiders even with mild wobble.
Mine is over 7 years old and has no degradation in his quality of life. He is in a very relaxed environment and as such he rarely corkscrews unless he is excited.
You say he was rescued so is it possible he is under stress currently?
Is his corkscrewing worse than this (jump to 2 minutes)? This is mine corkscrewing because he is having fun. Give your snake a chance to calm down. You rescued it so it is your responsibility to reduce it's stress