Boy, that's a real crapshoot as to whether it will work or not. I'm not sure exactly what checks you did with a multimeter on the motherboard, but it's entirely possible for the power input section to be fine but another part, say the CPU, to be non-functional.
No response on connecting it to a computer, I take it? That right there is a fairly good test, since it requires minimal functionality to be recognized by the computer, so if you're not even getting that, it's not a good sign.
A parts phone would be valuable in diagnosing the issue with your phone if you don't mind spending the money. At the very least you could swap motherboards and see which one comes alive when you do that. But if you really need the data, you might have to start considering professional repair or data recovery services.