Macbook stolen after I erased it - is data safe?

As to your initial query: Is my data at risk?

If you erase an SSD drive, you data are gone. There is no software solution that can bring it back. your data blocks were TRIMmed and queued for erasure, which would happen within a few minutes. If you then re-installed MacOS after erasing, you wrote over 350,000 files and re-wrote about 20GB of data.

Only spy agencies have the resources needed to reconstruct a very small portion of your data. They would need to have good reasons to spend a few months to reconstruct a portion of it.

You are perfectly safe.

Unfortunately, you followed incomplete instructions since you did not disassociate it from your Apple ID and you were still able to enable find my mac. what that means is that the thief can’t use it, and it also means that your intended buyer would have needed your Apple ID and password to update apps or reinstall.

For future reference please make sure to review BobtheFisherman’s link to the complete instructions which include disassociating the device from your Apple ID.

Erasing and reinstalling takes care of the OS, but unless you followed the steps in BobtheFisherman’s link, it is still associated with your Apple ID. If it wasn’t you would not be able to see it or communicate with it - it would not show up at all.

This is what needs to be done before selling a Mac: What to do before you sell, give away, or trade in your Mac - Apple Support

what model 13-in MacBook Pro by year, early mid late, and processor speed?

what type of drive (rotating or SSD) original or replacement, and what size?

I could be wrong, but offline just means the thief is not online. If you disassociate it, it would not show up at all.

I think babowa is correct.

The association (that allows "Find My Mac" to work at all) is with your logged-in Apple-ID, not with the serial number or anything else.

Yes, but then you will no longer be able to communicate with it. It should no longer show up on your other devices, under your Apple ID, etc.