for example if I have five or six blogger account under blogger.com, can I publish Google Ads those site? is it against Adsense TOS??
You can have as many as you want Bloggers account, but don't try to open more than one Adsense account!
Just open more, its just like having multiple websites. they cant expect you to have a blog on just one subject. I think I have about 20 blogs ( i never update them anymore)
Yes it's fine, you have unlimited space. Just make sure that you add URL channels to monitor each blog.
you sure can do that. Watch out for url channel. Google only give you 200 url tracking channels at the time.