Hi there,
I am an expert Javascript developer with more than two years of experience. I can develop what you are looking for. Here are my thoughts:
1. For project 1, it can be easily done. Just share the name of the website and which button you want a overlay on and I will demo this. This is trivial and I can do this for $30.
2. For project 2, I believe an extension will not serve your purpose. If you want a program to check a website for a certain piece of information and want to store it (in a file or a database) then you need a script that checks the website on a timely basis (everyday, every hour, etc.,) and store the information you need. Extension will not work if the browser is not on. So you need to activate the extension every time you want to check by opening browser and click on its icon. I can develop the script for $110.
To get started, share the URL for project 1 and 2 and I will be delighted to get started. Thanks for your time and consideration.