If his agent is comfortable that the NCAA will not levy lack of institutional control etc, consider Dan gone. If he stays, you can rest assure Penn State will probably be in a world of hurt.
Maybe he tells them he really wants the job but is worried about the NCAA and that he'd rather hang here where he likes it for now and would be more than willing to entertain an offer from them in the future.
I want to keep this guy at all costs. He's done everything we've asked him to do except win the big game. We're going to two straight bowls, we're expanding the stadium, we've built new facilities, and we've beaten OM 3 times in a row. Anyone that wouldn't be extremely upset at losing him needs to recheck their commitment to MSU.
..Penn State successfully sweeps under the rug the fact they had an assistant football coach molesting children on the Penn State premises for years, that will impress Dan Mullen to the extent Dan Mullen will accept the Penn State job.
I hope you realize the caveats you just set out for Mullen taking the Penn State job will mark Mullen a scumbag if he does take the Penn State job.