Hello,
I also faced the same set of problems.
I wrote a tool ImageNet downloader which uses the URLs to download ImageNet images. It takes good URLs and skips the bad ones. You can specify how many classes you want and how many images per class you want.
I also wrote a blog post where I did a little analysis of the state of the ImageNet URLs and came to interesting conclusions. It’s and 2011 URL list and many of the sites are down. You can check out the plots.
Hope it is helpful.