That turned out real nice, Mike! Those chains should hold up for quite a while.
Over the last 20 years we have replaced a lot of chains. Couple hits with a 44 mag 240 solid lead bullets wrecks the hell out of them.
Your weak point is the stud sticking out the back too long. Couple hits on the chain will break the stud off. I would bolt the chain directly to the target plate and use a large washer under the nut.
IMHO.
Used to shoot 5,000 rounds of full load 44 mag 240 gr lead bullet rounds per year when Ohio OK'd pistol hunting. My buddy Dale and I shot every Wednesday and Friday at a 6" steel target at 50 yds. Our average got to 9-10 hits out of 10 shots.