Steven,
I think you'll find the 200 l/mm gratings are very similar - see this test report:
https://spectroscopy.wordpress.com/2...ssion-grating/
Hmmm, Vega Planck curve - not really....
Yes, you have to use common sense and work away from the Balmer discontinuity - K. Robinson in his "Starlight-An introduction to Stellar Physics for amateurs" gives a very good explanation of the issues/ problems of a Planck curve fitment. (His other book "Spectroscopy - Key to the stars" is also recommended.)
IMHO I'd crop the spectrum below 385nm for the IR curve....safest way to start is with an A type spectrum which is easy to analyse and process.
(BASS Project contains a vast collection of element lines to assist analysis as well as the Pickles and Miles reference star database.)