I also have some experience with an 8yo and the Ruger (I'll need to check which model... similar size to the Mark III Hunter but black)...
IMHO, even a lightweight pistol will be heavy for an 8yo....
After a few shots, even a 1.5 pounder will feel heavy and get wobbly.
For safety, I'd start off with a bench rest and let him work on hand-eye, aim, trigger discipline, etc. From the bench it's much easier to manage safety.... He'll be less likely (and easier to stop) to turn to your voice or turn to a distraction and wheel the gun around with a finger still on the trigger. I'd avoid any work on "stance" until he had some level of comfort, reasonable ability to sight/aim, confidence (not over confidence) and good trigger discipline. At that point, he'll be able to handle a few shots competently without the bench. The needed arm strength will come with practice.
IMHO, YMMV, EIEIO
I am not a lawyer. This is NOT legal advice.! Nothing tempers idealism quite like the cold bath of reality.... SQLGeek
I cut my teeth back in the 70's on a 4" Ruger Mark 2, and taught my girls how to shoot a handgun around 10ish with a Ruger MK2 with a 6" barrel, which i still have. I love it and would highly recommend.
I start kids (my children and now my grandchildren and friends kids) with a single action revolver. Then we can go to a self loader. I have S&W 22A, Ruger 22/45, Colt Woodsman, and RIA 1911 with 22 barrel and slide. The Colt is the lightest, but I let them hold and try various guns until they are comfortable. We go the our range at the farm 2-3 times a month minimum and I try to let them shoot something new to keep their interest up. They also get to learn the manual of arms to more guns. It is always interesting to see which rifle or handgun they consider their favorite.
Yes I like pellet pistols and rifles, but they need to start shooting powder when they can handle the responsibility and the weight of the gun.
"A gentleman will seldom, if ever, need a pistol. However, if he does,he needs it very badly!" Sir Winston Churchill