Superman has done roughly the same numbers either way, so that "sells better if not married" thing doesn't fly (pun intended ). DC tried that. Repeatedly. And those sales patterns say more about the demographics and mentalities that the comics industry panders to than it does anything.
Clark doesn't only care about Lois. Even recent history under Bendis shows that. He cared about Kon (who he doesn't remember), he cared about Melody Moore, he cared about Robinson Goode, and just before Bendis he even showed compassion to Hank Henshaw.
As for "Lois dies and Superman goes insane" is the only thing you think Lois has contributed in recent years, that says two things: one, that DC writers are failing Lois as a character (which we all kinda know already), but also two: it's not even accurate. Jurgens had Lois going after Intergang and Rebirth in general showed that Lois is no pushover when it comes right down to it (and not just in a Bat-suit, either). Could they and should they be doing a lot more with her? Yeah, absolutely. But that they aren't is a failing on them, not a failing on her as a character or her value to both herself or Clark (as a character/partner) and the Super-verse as a whole.
And... you say Lois is "a bad secondary character," but also "the most important secondary character in history" - do you not see the conflict between those statements?
Didn't work for me, so they must have fixed it. All I see is the short crappy Justice League, not the long crappy Justice League, lol - and Tom And Jerry just plays Tom and Jerry (which was decent, btw).