If a vendor does not pay for the software I developed for them, would I be liable for throwing a "kill switch" to disable it?

You should contact an attorney in your area to seek payment for your work. If you disable the software, you could be liable for any damages...

It depends on the content of the images. Generally, if you are searching online and come across an image and view it there, you are not infringing...

Please I DESPERATELY need Help, am trying to raise money for college, but is what am doing LEGAL? Am so cared of Law Suit.

What you are doing is illegal and amounts to copyright infringement. The book publishers have software that can locate people doing exactly what...

I have an online website and want to sell replica handbags. Is this legal if i state that they are replicas?

No- it is illegal to sell counterfeit goods, even if you state they are replicas. You would still be violating someone's trademark and profiting...