First off, I appreciate the in-depth response. This was very informative.
I'm interested in Shazam for a few reasons. First, contrary to what you said, I was under the impression that he fared well against Aquaman. He doesn't care about his trait and his horrible wakeups make the oki game even more in Shazam's favor. As a Batman main, this seemed like a suitable alternate to use in this MU. However, if Aquaman is actually one of his worst matchups, then this reason is nill. Second, I think Shazam's combos are the best-looking in the game, and would enjoy using them. Third, I've been interested in picking up a lower tier character and trying to make them viable. Fourth, I'm definently a more patient and conservative player, and it seemed like this type of play is what Shazam demands given his lack of mixups (but I wanted to confirm this with question 5).
I'm still just messing around with him at this point, haven't yet decided if I'm really going to invest.