Working is likely a not possible, or at least annoyingly tricky.
You already have to best route figured out by using the B1/B2. Come here for a while, get to know your partner, their life, their city etc etc. You won’t be able to work but honestly you wouldn’t learn all that much from it anyway.
I did this kind of thing on a ESTA when we were LDR. The long stay got a little more scrutiny at the PoE than normal, but ultimately it was fine. Just be honest in all the questions they ask, make sure you bring plenty proof of ties to home country, have a return ticket and plan on leaving well before the expiry of your I-94!