Don't think nollie 180, just straight nollie, there's basically no turning involved.
Nollie nose start by going at a big angle.
Nollie crook is a good amount harder, will need to go much more parallel.
Would help if you could nollie fs 5050 the ledge (both trucks on same time, not a nollie 5-0 then put front truck down), that way you know you technically have a high enough nollie.
If your nose isn't getting high enough or you're clipping on the way up, you're probably popping with your weight completely over your nose and keeping your weight over your popping foot during the entire motion which makes it a lot harder for the nose to get high enough.
Gotta try and shift the weight a bit to your back foot after you pop, kinda like a see saw motion to level out the nollie, that way you can take weight off the front end of the board and let it come up a bit further... before you then put the weight back over the front to lock in.