Prospecting for broken backlink campaign.

I’m working on a project to find broken links in order to tell webmasters about a broken link and ask for a replacement with a blog post I’ve created.

This project would include researching potential webmaster's who will provide a backlink to

The two most important tasks are:

1) finding broken links that are on pages related to "starting a restaurant," "opening a restaurant," "mistakes when opening restaurant," "restaurant advice," "restaurant buying advice," etc.

2) THEN, finding all other pages which are pointing to those broken backlinks.
The link building method I'm trying to use is best explained

It explains how to use ahrefs and screaming frog (to find broken links and webpages where those discovered backlinks are also being listed.)

Please give a description of a plan you will execute the following

1) finding broken links in the "starting a restaurant" niche/area

2) find all other webpages with those broken links on their site.

If possible, please give an estimate of how many contacts can be provided and how much time it will require.