It's actually not that difficult to play. The pianiast probably has the more difficult part to play with parallel tenths (helps to have big hands). The clarinet and viola could have been a little tighter on the cadenza, especially the unison parts. Otherwise, a pretty good performance.
Don't listen to any of the "helpful hints". You're doing everything right and you're one of the most relaxed clarinetists I've seen. Stay that way.
As for the displacement of the clarinet by the saxophone - probably largely due to the be-bop era. That style is extremely difficult to play on the...