Ive replied to the questions you asked via PMs directly as PMs. Not sure how you want to proceed, either PM or in this thread. Gets a bit disjointed if its a mix, and PM doesn't give other people the opportunity to chip in. Ive never personally experienced algae like you have so i can only advise what i "would" do in your situation, not what has worked for me in the past.
There is a lot of neglect going on there, and im sure there are issues beyond algae. The algae is just the end result of all the neglect. While you can manually remove it or otherwise treat it, ongoing good practice and proper tank maintenance is the long term answer. But, it isnt your tank or responsibility.