The first part of your post is absolutely correct:
"That's the difference between being confident in your own abilities and being fearful that somebody is better than you. As far as I can tell Saban has gone out and hired the best people he can find to fill positions on this coaching staff, even people with far more NFL coaching experience than he has so, it doesn't sound like he'd be the type to be afraid to keep Rick Speilman if he decides that Rick is the best person for the job....."
So if he does let him go, knowing what we know from Saban's time here as detailed above so well by you, we can only assume either Saban doesn't hold a high opinion of Spielman, or, Spielman thinks in his own mind he's too good now to be an underling and is unwilling to take a pay cut appropriate to the limited level of responsibility he would hold. If he stays then Saban must think he has some value to him as an assistant.
Either way, Rick Spielman is not really very relevent here anymore, the decision maker is Saban, he is the one who will take the blame for poor drafting and he is the one who should be credited for improved drafting as we saw in this most recent draft, perhaps one of our best ever.