He felt-------

He felt it would be unrealistic, in view of the intense turmoil that would likely follow, to make the sacrifice required in order to gain such little advantage.
The problem with the meaning of the underlined part specially with the bold part.

  1. What is the meaning of the underlined part?
  2. Please explain the pattern of the bold part with more example.

Turmoil means trouble or inconvenience. Likely means probably. “That would likely follow” means something will probably come next, or it will cause something to happen. So he does not want to make the sacrifice because it would probably cause a lot of trouble and hardship, but would have little benefit.