Client disappeared for five and a half years, wants to finish the project now

Hey everyone,

I'm looking for a little bit of input on how to handle a weird client situation.

So, five and a half years ago (the summer of 2019, to be more specific), I started a project for a client. The project was to typeset/format a book he had written and was planning to self-publish. I gave him a quote, got 50% of the money up front, and did the initial typesetting/formatting of the manuscript in InDesign. 

We got into the correction/revision phase, and then he went silent. He was an older guy and had already had one massive heart attack, so as time went by and he never got in touch, I figured he'd passed away. Since he had only paid 50%, but I had only done part of the work, I was fine calling it even.

So imagine my surprise when he popped into my inbox after five and a half years and said he wanted to finish the project.

That wouldn't be so bad, except, like I said, we're at the revision phase, and he's sent me a Word file with so many changes and additions that it would be enormously time-consuming and error-prone to go through and do them all by hand. It will be easier and probably faster to start over from scratch.

The problem is that we didn't have a good conversation (in 2019) about how we would handle the revision phase, nor did I have a contract that stipulated anything about what would happen if he disappeared and emerged later.

I don't feel like it's reasonable for me to pick up where we left off, especially given the mess I have to work with regarding his manuscript. But it also doesn't seem fair that we ignore the money he paid me in 2019 and start over with a new quote.

The truth is that I'd rather not do the project at all because although he's a sweetheart of a guy, he's also challenging to work with (too disorganized, wants too many phone calls to discuss things, etc.). But in that case, what do I do with the money he already paid me? I did a lot of work, but he doesn't have a finished product.

Any thoughts?