DMI is intentionally designed to massively exaggerate the effect of game shape. So in general, equal DMI doesn't mean equal performance in any respect.
No, of course not. But since Player's A two skills at Prominent take bigger share of his DMI than rest of his skills, we can say that compared to Player B, Player's A relative skills look like this:
6, 6
8, 6
6, 8
6, 6
6, 6
This is an educated guess of course. But if it was true, I would probably pick Player B.
3) As for your last question: I find it to be completely dependent on the circumstances, opponents' tactics, tendendencies (e.g. what do they play at SF? more important to protect the perimeter or to protect the paint and rebound?)
To exclude those circumstances, let's say both teams are the same on PG, SG, PF and C spot with same GS, playing Base offense both. Opposing SF is Respectable on every skill.