JR is not crucial for a PF, but it's pretty nice to have. Pitiful won't hurt too much, but getting it up to mediocre or so would be a good idea.
I consider Driving important for a Forward. It's cheap, too. But yes, you'll want some driving for a Forward, not only to reduce .turnovers (1 on 1 does also train handling considerably), but also to get easy open layups. That's particularly true for fast-paced teams, but even with slow pace you want some slashing from your PF.