UPDATE 2019-12-04: Since very rarely developer needs actually Dead Keys, I took the liberty to remove the Dead Keys (as I wanted easy Backtick and Tilde).

The modified keys are as follows

• Option+ä will result in Caret (^) symbol
• The key left of 1 now produces Backtick (` ) and Tilde (~) without Dead state. ← Happy Gmail Section navigating 😉
• Key next to Backspace now produces acute accent (´) and grave accent/backtick (`)  without Dead State
  • The same key has Dead Key state with Option (⌥) key.

Installing

1. Download the EstonianDevNoDeadKeys.dmg file (sorry for the .zip – WP does not allow .dmg files to be uploaded directly)
2. Unzip and mount the image
3. Drag the EstonianDevNoDeadKeys.bundle to the Keyboard Layouts folder linked into the DMG
4. Add the new layout from Input Sources
5. Enjoy!