You mentioned cutting it free of the stump, then talked about using wedges. Seemed unsure of a hinge. Either you aren't really sure of what you're doing or you're having difficulty explaining your plan. Either way, you should consider giving this a pass. Your family doesn't have the funds to hire a pro, do they have the funds to fix their power lines?
The pics show (i think) that the fir(?) is between the birch and the lines. If that is the case, a pro would just climb the fir and rope down into the birch and block it down. He's safely tied in and the power stays on. No fancy equipment needed (unless you call a rope and harness fancy). Seems way easier to me that trying to set up pulling lines attached to vehicles.
The pics show (i think) that the fir(?) is between the birch and the lines. If that is the case, a pro would just climb the fir and rope down into the birch and block it down. He's safely tied in and the power stays on. No fancy equipment needed (unless you call a rope and harness fancy). Seems way easier to me that trying to set up pulling lines attached to vehicles.