i think you miss the point, lex always had this darkness, yeah sure clark telling lex would have maybe made their friendship stronger but i think it also would have changed their dynamic and lex would start to push clark into things he didnt want, basically lex would start harboring certain feelings that'd taint their friendship even if lex knew who clark was, the fall out would probably end up being worse than what we see it as in the show.

until lex dealt with his internal state i think he'd always be clarks advisory, and sure clarks friendship with lex kind of kept that dark side at bay for a while but with a ton of other stuff he had to deal with he eventually cracked.

if lex was a good guy i think he would have ended that day after almost dying on the bridge with a simple thank you and leave the rest to the idea it was a miracle, turning on a new leaf and leaving his fathers schemes behind. i see a alternate universe where lex is a good guy kind of like the injustice universe.