I have dived it about 15 times, just only once in my boat. The Spiegel is an easy wreck in my opinion, I am more worried about my son, even though I shouldn't be cause really he is a better diver than me lol (even though he has a lot less dives) He is already free diving to 70 feet and holding his breathe for 3.5 minutes.
But because of his age, obviously will be cautious.
I didn't say you weren't qualified to dive on the wreck but inside the wreck. Are you overhead trained? Have you had cave/wreck training (not a PADI specialty)? Are you diving with redundant air sources?
Not sure what free diving and breath holding has to do with being a better scuba diver. I'm more concerned about being able to resolve issues without panic, and more importantly, being able to avoid issues in the first place.