Jansport is a common type of backpack, especially for school. By “go to school with this”, Tyler means he’s “teaching” the kids with his music

This could also be a reference to the backpacker subculture which got its name from graffiti artists who would carry their albums (reference in previous line) and their spray cans in a backpack. It is now used to describe underground, alternative rap

The “go to school with this”-type lines that end each verse could be interpreted as “just try going to school with this sort of burden”, since there is evil in the backpack, and the lines that follow are about general hardship

The line is self explanatory except for “hoy.” This is Spanish for “today.” In the following line he uses “soy” which is Spanish for “i am.” Substituting in Spanish words fulfills his rhyme scheme and makes the lines a bit more confusing to compliment his “confused boy” theme.

He is also stating that he is bad for kids to listen to because of how vulgar and explicit he is in his songs.

He may be saying oy as in oy gevalt which is basically something a person says when they are stressed.

Nice metaphor here: Stuffing is weed, the oven is a pipe or a joint, and getting baked is, well, getting baked.

This could also be a reference to cooking with weed. B.o.B is making pot muffins (though pot brownies are much more conventional).

Lupe doesn’t rap about selling drugs because he sees it as being something that is a bad influence on his fans and he says it would be labeled as a “bad track” in his opinon.

I think he says “…and I ain’t tryna back back” because, 1) he is continuing the idea that he doesn’t want to backtrack, and says he doesn’t want to back (as in walk backwards) back (as in backwards in time or as the better person he is now). And 2) I think he just repeated “back” twice because he had to fill the bar, or measure, for that line.