Short answers, pulled from the story.
Ringo Starr established Startling Music in 1968 to secure financial independence from Northern Songs. The company was originally set up by publisher Dick James and manager Brian Epstein on behalf of the band in 1963.
Ringo Starr created Startling Music because he felt under-promoted and received second-class treatment compared to John Lennon and Paul McCartney within Northern Songs. He chose to leave rather than accept terms that offered only about 1.8% ownership shares while others cashed out during the ATV buyout in 1969.
Startling Music published Don't Pass Me By and Octopus's Garden which came from the Beatles final albums. The firm also managed royalties for Starr's solo hits and co-written material including his 1970 country album Beaucoups of Blues.
Ringo Starr received part-ownership shares totaling about 1.8% of the venture when Northern Songs became a public company. This arrangement did not provide enough incentive for him to re-sign with Northern Songs given that John Lennon and Paul McCartney owned about 15% each when they renewed their deal in 1968.
Vini Poncia became a longtime collaborator who helped shape new material for Startling Music after Ringo Starr established the firm. George Harrison continued to team up with Starr on various songs following the split to protect their financial futures.