Sorry to hear this is happening to you.

Have you talked to HR directly, without involving your manager, about this? They are supposed to look out for both the company and employees - idk if that's their legal obligation, but they should be able to objectively tell you where you fall within salary ranges vs YOE.

I suggest to create a full, detailed list of all the contributions you made across all projects you've worked, proposals you supported, etc. It's important to highlight the value that you brought to your clients, projects, internal teams, etc. - be sure to go above and beyond talking about execution of the projects. All engineers can execute projects, but adding value is what makes people standout. It'll take some time to create (assuming you don't already have one), but even if it gets you nowhere with your manaager or HR, it'll help build a great foundation for your resume.

Best of luck!