Im sorry for such a late reply, but mashAllah your question got me thinking, jazzakAllah Khair!
I do understand your confusion, but with this ayah the difference is that the letter "Laam" is not like the other "Laam"'s by that I mean its not the normal "Al" Infact the Laam is part of the word! Its root word is "Laffa" meaning to "cross" something with something else, due to this reason the "Laam" must be pronounced. :brother:
As for the maad question i'll come back to it inshAllah, just need to find the kitaab lol