Snowballs and Armor Stands in post-1.11 [duplicate]

So I was trying to make grenades and I used an armor stand tracking command set I found here How would I make something spawn when and where a snowball hits something? (MrLemon's answer) and it has an issue for me. After converting the commands from pre-1.11 to post-1.11 format (e.g. Snowball to minecraft:snowball) the armor stands won't leave and once the /summon tnt command goes off, I get a huge row of explosions along the trajectory of the snowball. I tried something like

execute @e[type=snowball] ~ ~ ~ summon armor_stand ~ ~ ~ {NoGravity:1b,CustomName:"SnowballMarker",Marker:1b,Invisible:1b}

testfor @e[type=armor_stand,CustomName:"SnowballMarker",Marker:1b,Invisible:1b] {inTile:Air}

kill @e[type=armor_stand,CustomName:"SnowballMarker",Marker:1b,Invisible:1b,inTile:Air]

First command summons an armor stand at the snowballs location.

Second command tests if the stand is in the air(at least that was the plan)

Third command kills said airborne armor stands.

If anyone can make a post-1.11 friendly version of MrLemon's command, I'd greatly appreciate it.

Also, please show the arrangement of the commands in their command blocks, crazy things can happen.