I'll give you some leeway because you are new here (let's hope I don't get chastized for that).
Also because I think you have a fair idea what you are doing, but you stumble because you are going too fast.
Again, ##\vec E## is a vector. I've drawn the two contributions from the +Q and the -Q in the figure.
There are no other contributions, so the field at P is the sum of these two. The vector sum, that is. Your job to do this vector addition. Andf yes, x/r appears in there (not x/R but x/r; I don't see or know of R in your post. Work accurately

). And yes, it's downwards. Easy exercise, but a good vehicle to learn to work systematically.
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