Found some of Shooter's comments on Secret Wars II on his blog:

Has Shooter ever taken responsibility for the unnecessary grief he gave to top talent during his years as EiC?

-C!

I recall being very excited at the prospect of Sal Buscema being assigned to SECRET WARS II... then being sorely disappointed that Al Milgrom was his sudden replacement.

But although Milgrom is nowhere near a favorite of mine, I ultimately found his pairing with inker Steve Leialoha to be a surprisingly solid combo.

Jim Shooter was 24 years old when he was on staff at Marvel as editor and writer. In 1987 Marvel terminated his employment. He was young, (24 through 36), enough for his success to fuel anyone's ego. Young enough and perhaps greedy enough to overreach his capabilities. A trait common in many, both young and old.

I truly wish he had wrote more and edited less. But given the loss of so many of Marvel's writer-editors in the 1970s, it might have meant step up or get pushed out.

Many of those that were present back in the day seem to opine that Jim Shooter was basically "good for the first few years" as he pulled Marvel together from the shape it was in in the mid-70s. 

I remember prior Ed-in-Chief Archie Goodwin saying something to the fact that "Star Wars kept us alive" around 1977 or so.

Your detailed complaints about Shooter are well documented and detailed.

My question(s) is(are) this(these):  

When was it that Shooter turned and became more an obstacle than benefit?  Was it circa 1980? Or was 1982?  

Or was it more toward 1985?

Or was he always more of a problem from the beginning of rising to Editor-in-Chief of Marvel?

I figure you have possibly the most apt insight of anyone having been in the center of the action as Marvel turned around.

LINK: https://www.upress.state.ms.us/Books/J/Jim-Shooter2

"Included here is a 1969 interview that shows a restless teenager; the 1973 interview that returned Shooter to comics; a discussion from 1980 during his pinnacle at Marvel; and two conversations from his time at Valiant and Defiant Comics. At the close, an extensive, original interview encompasses Shooter’s full career."

LINK: https://www.upress.state.ms.us/Subjects/Comics-Studies