I'm in agreement with you, in that I think I've seen enough of Davidson. Palka would be more interesting if he could field a position to the tune of "only" -5ish DRS, but alas, he's a butcher. Oh, and get his Ks below a ~33% rate. For Delmonico, he's quietly built himself back up to a ~95 wrc+, and with health & more exposure, perhaps he can become more. At the same time, while Delmonico isn't who I'd want @ 3rd, he at least has exposure at that position, and could be an "emergency" option, behind a FA signing, Yolmer, and perhaps Leury.
Insofar as the bolded goes, I have to disagree. Engel looks like a typical "Garbage Time Hero" who will promptly go back to sucking at baseball, as any number of GTH's have done for the SOX in the past. I've been done with him for months.