Welcome to the pit :smile:
First thing I recommend you do is stop using the SDK folder structure
for holding your maps and everything. I've never quite understood why
they bothered making hammer use it to be honest, as to me it comes
across as confusing and unnecessary, but I guess its meant to keep your
official HL2 folders free from clutter. You can set it up by modifying
the below screenshots to match your steam installation...
Obviously the place you store your hammer maps (the parts listed with
the path "c:\development\source\hl2dm") you can change to wherever you
like, bu make sure you have a gameinfo.txt in that folder. Also note
that you will have to change all my HL2DM setup stuff to HL2, but I'm
sure you can see where that is necessary.
Once thats done, hopefully you should be able to run your maps properly
through HL2. This should, I assume get rid of any of the error messages
you are finding yourself with in the game.
Your light_spot however is not working for a different reason, though
what they reason is I'm unsure. Try looking at the light_spots used in
the source file of dm_lockdown for ideas on how to get them working
properly, they can be tricky to get working at first.