The nub appears to be a root. See how it has split the leaf base just like the root below it. A spike would normally emerge in the leaf axil, above the leaf.
The yellowing leaves look like normal aging and senescence. Nothing to worry about unless it become a rapid progression of additional leaves up the stem.
I see no reason why it shouldn't be a perfectly happy plant in an empty coconut fiber basket. In fact, that seems like it might be better if you're growing in a sometimes low humidity indoor environment. Just make sure the fiber dries out between waterings. I think the roots will find their way through the fiber if they want to, but some slits wouldn't hurt either.
Healthy plant. Smart questions. You're on your way...