Well, I can tell you that Salesforce has a very capable and robust API. I’ve done some integrations involving Salesforce, Google Apps Script, and WordPress. It might be worth exploring the possibility of integrating with your partner company’s Salesforce data via API. Salesforce is BIG on security, but there are ways to set up “trusted” apps within Salesforce. In other words, it’s certainly “possible” to create an automated integration between Bubble and Salesforce, but it would likely require some setup and dev on the Salesforce side. Perhaps you’ve already looked into it.
I hear you about the import issue. That’s pretty frustrating. Here’s a post by someone who imported more than 3 million records, but that was a one-time deal.
EDIT: FWIW, it would be pretty straightforward to automate the import of data into a Google Sheet using Google Apps Script (GAS).