I can almost picture this Van Helsing secretly collecting insects, and eventually offering them along with his hot cocoa as they travel. Just in case Renfield prefers them, so he won't starve.

I find that so incredibly poignant, I think you should write it. I can imagine Jack Shepherd's Renfield carefully preferring cocoa, no matter what he actually wants.

I do wonder how Renfield would react to the Brides trying to convince Mina to come to them...

My first thought is that he would have wanted her kept safe as in canon, but then how difficult to witness someone else—who doesn't want it—invited into the very camaraderie you are trying so hard to resist yourself. Would they appeal to him, too, to help convince her? Or is he no longer of interest, having fled Dracula's commands?