Here's how to level 3 cheese Nasus with Jax. Note I pull this off almost every time. I run 27 offense 3 utility on Jax. AD quints, hybrid pen marks, armor yellow, and CD glyphs. You can start red pot or not, but red pot makes it way easier.
Start AAing minions immediately and rush lvl 3. You want to time it so the wave is still about midway in the lane and you hit it right before him. Every time he tries to CS and you can, use an AA > W combo and if he used his Q and you don't have a lot of minion aggro, KEEP hitting him. Try not to use Q as it burns mana you will need to do your full lvl 3 combo.
The second you have lvl 3, start your combo. If you get AA > W > AA in and he hasn't run yet or tried to trade, he is 100% dead.
Ignite, pot, and ghost. The trick is to time the stun so he can't flash it. If he also took ghost/ignite, he's totally dead. Even if he withers, you have your jump.
If for some reason he gets out, he'll have to base and lose a ton of cs to the tower. Grab a dorans and the lane is a nightmare for him from there as long as you bully as hard as possible.