Just for clarity, ~ is a short cut to /Users/your_account_username, you'll also encounter $HOME, same thing [1].
~/Library == /Users/your_account_username/Library
We saw the same error on our OS X 10.6 MacBook.
Here's a freshly-compiled OS X wallet, works on 10.6, should work for you on 10.7 -
http://minkiz.co/noodlings/cdt/Detkoin-Qt-OSX.zip (referenced on
http://minkiz.co/noodle)
Don't worry about creating directories. Fire up the app, it will create the directory:
~/Library/Application Support/Detkcoin. As soon as the wallet appears, that's it for this stage, you can shut it down.
Now fire up a text editor, paste the contents of the detkcoin.conf as listed in the OP and save that as
~/Library/Application Support/Detkcoin/detkcoin.conf and then restart the wallet, should start syncing, doesn't take long to get up date, just a few minutes.
To try mining, select Menubar->Help->debug window
debug window shows two tabs: tab1 is info, tab2 is rpc terminal. In the commandline window at the bottom of tab2 enter
setgenerate true -1 for all-in, chuck everything at the hashing. Or use positive integers to limit processing to use that number of threads/cores, e.g.
setgenerate true 2.
Stop mining with
setgenerate false.
HTH.
Graham
[1] there’s no place like $HOME
Edit: corrected config filename, added stop mining info 
) 
I'm running 10.7.5.