You need to think with Portals!
Look up in the direction you are heading to the fire; you can spawn a portal on the wall up there, one to your right, and teleport out of danger.
After that, keep trying to reach the party to get your promised cake!
According to the ASCII art it's "GLADOS"
Check this page. Look at the second post, click Show and scroll down to GLADOS you'll see the same ASCII art there in reference to that name.
EDIT: In case that page goes away here it is
"GLADOS1" "[12.000] #+ @ # # M#@ "
"GLADOS2" "[12.000] . .X X.%##@;# # +@#######X. @#% "
"GLADOS3" "[12.000] ,==. ,######M+ -#####%M####M- #"
"GLADOS4" "[12.000] :H##M%:=##+ .M##M,;#####/+#######% ,M#"
"GLADOS5" "[12.000] .M########= =@#@.=#####M=M#######= X#"
"GLADOS6" "[12.000] :@@MMM##M. -##M.,#######M#######. = M"
"GLADOS7" "[12.000] @##..###:. .H####. @@ X,"
"GLADOS8" "[12.000] ############: ###,/####; /##= @#. M "
"GLADOS9" "[12.000] ,M## ;##,@#M;/M#M @# X#% X# "
"GLADOS10" "[12.000].%= ######M## ##.M#: ./#M ,M #M ,#$ "
"GLADOS11" "[12.000]##/ $## #+;#: #### ;#/ M M- @# :"
"GLADOS12" "[12.000]#+ #M@MM###M-;M #:$#-##$H# .#X @ + $#. #"
"GLADOS13" "[12.000] ######/.: #%=# M#:MM./#.-# @#: H#"
"GLADOS14" "[12.000]+,.= @###: /@ %#,@ ##@X #,-#@.##% .@#"
"GLADOS15" "[12.000]#####+;/##/ @## @#,+ /#M . X, "
"GLADOS16" "[12.000] ;###M#@ M###H .#M- ,##M ;@@; ###"
"GLADOS17" "[12.000] .M#M##H ;####X ,@#######M/ -M###$ -H"
"GLADOS18" "[12.000] .M###% X####H .@@MM@; ;@#M@ "
"GLADOS19" "[12.000] H#M /@####/ ,++. / ==-, "
"GLADOS20" "[12.000] ,=/:, .+X@MMH@#H #####$="
Best Answer
I guess you have found this thread, they suggest a variety of methods for getting rid of the music, and one of them is replacing the looping_radio_mix.wav that you mentioned.
Could you describe how and where did you look for it, what else did you find (if any), or where does Steam keep its files on a Mac?
If all else fails, try voting and commenting on this Github issue, and hope you are raising the developers' attention to the problem.