I think you are right. My computer is 12 years old and hobbles through everything, I was trying to limp through this year with it and I probably clicked through something like an idiot to get things done without paying attention and now I have fucked myself over. I absolutely hate Microsoft for forcing this down everyone's throats, reddit is filled with horror stories like mine with this exact issue.
Looks like I will need to find a cheap replacement machine and install Linux mint. Hopefully it can run Onshape and Fusion well enough.
Unfortunately I was never able to get my device in my Microsoft account. I spent two hours on the phone with them two days ago, they couldn't do a single thing to help at all. I'm now trying to find anyone that can brute force their way through the BitLock, I would be willing to pay for that.