Electronic configuration of Ace-Ala-Nme
1: sp3 with 1 electron withdrawing group
2: sp3 with 2 electron withdrawing groups
3: sp3 with 0 electron withdrawing groups
4: sp3 with 1 electron withdrawing group

I would say your earlier analysis was correct.  If you look at the resonance structures that can be drawn for an amide linkage, you find there is considerable positive charge both on carbon and nitrogen.  This should serve to make them both electron withdrawing, relative to an attached carbon, in your structure.

EDIT: To clarify this answer with regards to some of the comments posted above, I'd like to add that typically when an amino nitrogen is situated on a double bond or aromatic ring it can donate electrons through resonance.  In fact, that is what it is doing in the resonance structure on the right - it is donating its lone pair of electrons via resonance.  However, the amino group is also electron withdrawing in an inductive sense relative to carbon.  Further the $\ce{-NH3^+}$ group can no longer interact via resonance and is simply a strong electron withdrawing group.  The resonance structure on the right is analogous to the $\ce{-NH3^+}$ situation and since it is a significant contributor to the overall description of the amide (cf. there is significant double bond character in the amide $\ce{C-N}$ bond) it acts inductively as a strong electron withdrawing group for the attached $\ce{sp^3}$ carbon.