You need to have a certain amount of speed before touching a wall. Running from the ground towards a wall, then jumping would work as long as you don't touch the wall before jumping. Most of the time, whenever Mario's not clinging onto a wall, it's either that Mario somehow considers the wall as a thok barrier (which he can't cling onto), or his angle isn't actually in the angle range even he looks like he is for whatever reason. As for bonking on "nothing" whenever Mario jumps off a wall, Mario's Wall Kick angle range is more sensitive when he's in a Wall Kick state to make it easier to keep Wall Kicking. Mario just not jumping off sometimes is probably not jumping at the correct time because there were times when Mario just doesn't kick off the wall in SM64, which only gives you about 5/30 of a second to Wall Kick compared to this mod's 14/35 when just jumping at a wall.