Two questions about image resizer

Hi, here are my questions.

1) I create a "cache" folder inside a general "img" folder to store the resized images. After loading the page I check the folder img and I find an entire folder tree as it follows: cache/sullastrada (site root)/img/news/proportion/IMG_3417_w50_h33/ then the image.
Is it normal ? Does the extension recreates the entire tree folder from root to image ?

2) Imageresizer creates a thumbnail on the fly, and that's perfectly fine. If I have to delete the image the thumb was created from, is there a way to do so ? I try to explain what I mean.

I used ADDT. I Uploaded an image to the server and stored its name in the database. Using a behaviour called "show image thumbnail" (or something similar) on the page, I created on the fly a miniature af the original image. I could choose where to store the new image, its size, and so on... This is quite the same as Imageresizer does.
Then if I needed to delete the original image I simply used a "delete image" (or similar) behaviour and it retrieved the image name from the database, deleted the original image and each thumbnail that was created from that image. Everything worked completely automatic and nothing new was written in the database. I don't know how they did that, but indeed it was really a time saver feature.

This is one thing I miss ADDT. Is there a way to do something similar with your extensions ? If not almost the same, is there a way to do something "quite" similar ?
I'm asking so, because If I upload, say, 10000 images and generate 10000 thumbs, then delete those 10000 images... I will have 10000 thumbs, 10000 custom "IMG_3417_wXX_hXX" folders and who knows how many more folders and files.

Thank You