It had been specifically communicated to them mid-work about the scope of the work being changed and they agreed to it.
Anyhow, how did you miss the whole point of not even paying me the 300 that was promised in the "contract"? Please read the thread again. This isn't about extra 200 being demanded but not even paying the initial 300 as agreed.
This is his suggestion
I'll get another developer who can get all the docs from you and get it on my site and ill pay the 300 via escrow. If he can't use the docs then im not paying for it. Easy
If he says that he will pay you $300 if the documents are uploaded to the site and work correctly, he will pay you via escrow, so why don't you accept this solution? I think it is an acceptable compromise from my point of view, but if the scope of work is expanded and they agree to it, as you say, then this is another problem.