I think for your first map release you havent done too bad. I only went into god mode when trying to pass combine to turn off alarm (& yes snipers are tough).
Either beef up the weapons or lower the npcs skill, attack damage or just their general quantity.
Some of the lighting needs improving but,
thats not a major concern at the moment. Also the under water cave is ok once you subdivide you should sew and rough up the shape a bit more with paint geometry so its a bit more natural.
I think it's good and you are doing well so far apart from what's been mentioned.
Also smaller cable width, and add some burning sounds for fire at spawn.
Also:
You see where the verticals meet the horizontals the different width's and the middle vertical even goes into the middle horizontal.
Now I like the combine architecture you went with but on closer inspection some smalls mapping mistakes or bad practice.