Congrats on a tough set.
To answer a few questions-Comics were getting edged off the newsstands by magazines costing twice as much. Why sell a twenty cent comic when you can sell a dollar magazine or paperback.
Marvel came out with these as an alternative to DCs 100 page books. There were supposed to be two lines, a 52 page line for .35 cents and a 68 page line for .50 cents. The plan changed after a couple of .35 cent books were published. DC raised their prices to .60 cents and they contained mostly reprints, where Marvel went .50 cents with more original stories. Then they published some all reprint books after promising new material in the Giant Size line. Between paper shortages, WIN, rotating editors and the copious amounts of drugs being consumed, we were lucky to get what we did. I bought most of the books that featured heroes I liked, but skipped the Daredevil and Power Man ones- all reprints.
I got real excited when I saw GS Super Stars #1, with a new Hulk-Thing fight, and even more excited whn I read the plans they revealed inside. Sadly, they changed and not for the better.