Desperate: ISP bandwidth throttling crushing our SaaS?

Introduction & Urgency: Our SaaS is experiencing critical performance issues. We're losing users and revenue, and I'm at my wit's end trying to figure this out.

The Problem: Users are reporting extremely slow loading times, frequent API timeouts, and intermittent connection drops. This isn't just a minor annoyance; it's directly impacting our core functionality and user retention. We strongly suspect our ISP is the culprit, specifically related to bandwidth or throttling.

What We've Tried So Far:

• Server-Side Checks: Thoroughly reviewed server logs, database performance, and application metrics. Everything looks normal on our end when the issues occur.
• Speed Tests: Ran numerous speed tests (Speedtest.net, Fast.com, etc.) at different times. Results are wildly inconsistent – sometimes decent, sometimes abysmal, even within minutes of each other.
• ISP Contact: Called our ISP's technical support multiple times. The usual "restart your modem" and "everything looks fine on our end" responses. No real diagnosis or solution.
• Network Monitoring: Used basic network monitoring tools to observe traffic, but it's hard to distinguish between general congestion and deliberate throttling.
• User Feedback: Collected user reports from various geographic locations, but the pattern of issues seems more tied to our office's connection rather than widespread global network problems.

Our Core Questions (Seeking Your Expertise):

• How can we definitively prove that our ISP is throttling our bandwidth or causing these performance issues? Are there specific diagnostic tools or methodologies?
• What are the best long-term monitoring solutions for ISP performance that can provide irrefutable data for negotiation (or switching)?
• Has anyone successfully negotiated with an ISP regarding business-critical performance issues, and what strategies worked?
• At what point do you decide to cut bait and switch ISPs for a business, especially when tied into a contract? What should we look for in a new provider?
• Are there any legal or contractual clauses we should be reviewing in our ISP agreement that might help us out of this bind?

Call for Help: We're losing money and reputation every day this continues. Any advice, tools, or shared experiences would be a lifesaver right now. Thanks in advance!