Should I be concerned with my back flow valve pit filling with water?
The fact that the water is seen in the pit only after a rain is a good thing, meaning your water table is not the problem, because that would mean a sump pump for sure.  I think you are just seeing this because the valve is only 2' from the wall.  Normally, it was dissipating.  You had a good wall/slab system that wasn't leaking until a hole got poked in the slab for the repair

Some grading of the soil alongside this wall for better runoff might be in order.  Any drainspouts nearby? 

Some ad-hoc pump automation in the pit would give you some peace of mind until you can get outside for some landscaping.

Self contained sump pump  

To verify gutters-to-storm drain are intact and not leaking down at the slab level,
Put a bottle of easter egg dye into the storm drain connection.  If you see the color in the pit, I would disconnect the downspouts and direct them into the yard.  

A pain for mowing, but the flip up ones work well. In our area, downspouts were connected into the floor drains and thence to the sewer. In the 1990s, we had to cap the connection with concrete or face a fine.