Did you pick the right tower ? Using tower.turetRange is fine. It just needs to know wich tower.
Same for the bullets. You need a instance variable that identifys the bullet as shot with a particulair tower.
Then you have to pick the right bullet.
And it will not be an '=' comparing, but an '>" comparing.
But i am not sure if that is practicable. You can also use the expression > distance(bullet.x,bullet.y,tower.x,tower.y)
More about the picking:
First you need a for 'for each tower'. That will make the picklist contain one and only one tower.
Then comes a sub event that picks all the bullets shot by that tower. Since it is a subevent and it picks differend objects then the tower, it will add the bullets to the picklist. So now you have in that picklist one tower and all the bullets shot by that tower. Then comes a sub event under the last subevent ''bullet distance travelled' > 'd'. That is also in fact a pickcondition. Since it is a sub event, its takes the previous picked objects and filters them. So now in the picklist there is one tower and the bullets shot by that tower that traveld a distance biggeer then 'd'.