Pretty high given this is exactly how I would scrape and resell Google results (eg. for a SEO service) if I wanted to evade their automated abuse systems (stolen Google account credentials).

About 165%, just winging it here

This is using a Google API the way it's meant to be used, and the API offers up to 100 free requests a day after which you need to pay.

The odds of Google deciding to ban you for using their public API are presumably similar to the odds of them deciding to ban you for using their other public services. So maybe high enough that you would t want to build a business plan around it, but I'm not sure why you're specifically worried that a user would get banned from the whole of Google for using a Google API.

That's not the API-using part of the code, it's the part that pretends to be a browser, logs in, opens the "custom search engines" control panel and pulls the name+ID data. It's definitely not a public API.

Doesn't sound that dissimilar to what Google themselves do.