I had a Kano online doing that to me, Jump kick, air Grab or (when the normal jump kick is blocked) normal Grab, repeat.
Online makes it hard to time a response to this.
1. Don't play on a bad connection.
2. after being knocked down by grab or air grab, moves like ice clone or any wake up special must be timed so that they are registered as a wakeup move.
Wakeup specials have other properties than specials from a standing position. They are faster and have invincibility.
With timing ice clone could work not sure on that Slide may be better and is faster.
I've been slided out of jump kick attempts often by Sub and Reptile, Smoke's own :en shake works good against jump kicks too.
But keep in mind that wake up specials are often unsafe.
3. After having blocked a jump kick you don't wanna be thrown.
You can do attacks with a duck built in (called tech crouch) like d1, d3 or d4.
Uppercut may be too slow in the start up to not get thrown.
Sweep can be jumped over and punished with another jump kick or a jump punch i think.
You can also escape standing grabs by pressing 1 against normal throws or 4 against front throws when being grabbed.
A 50/50 chance dependin on which grab he does. But Smoke's front grab is better for knockdown pressure so you wanna use the 4 grab escape more often.
Unless your opponent is predictably using the normal one, try to read him.
Edit: i think you cannot hold block and escape at the same time like in Soul Calibur and other fighting games, in MK you must let go of block to escape a throw.