Nudges:
The ends of the theme entries are important.
(A)bide + (B)arbara = (C)rossword or, put another way: 1 + 2 = 3
If you have a five-letter word at the outset, that is NOT the answer. You need to decode the first word to find the correct answer, which is also five letters long.
Remember that first nudge? A=1, B=2, C=3 That seems like a possible code. Can you decode the first word using numbers in the grid?