I've loved and used Emacs for ~20 years, but if Emacs were to become slow, then if I were to have a replacement editor that could do the following (w/no X or window manager) without additional config in Linux, I'd use it instead:

  arrow keys to move
  add and delete text anywhere
  paste from terminal buffer
  ctrl-s -> search (and continue to find next match)
  ctrl-v -> down
  ctrl-esc -> up
  ctrl-k -> kill line
  ctrl-x ctrl-s -> save
  ctrl-x ctrl-c -> quit
  ctrl-a -> goto beginning of line
  ctrl-e -> goto end of line

Antirez, of redis fame, wrote a minimal editor in C which got a lot of love here on hacker news a while back:

https://news.ycombinator.com/item?id=12065217

I took that release and added Lua scripting support to it, which also seemed reasonably popular:

https://news.ycombinator.com/item?id=12137698

It pretty much meets your requirements, and was a fun project. But it did make me realize that writing editors is sometimes harder than you'd think.

  CTRL-S: Save
  CTRL-Q: Quit
  CTRL-F: Find string in file (ESC to exit search, arrows to navigate)

Kilua looks cool also as it has more similar keybindings to Emacs[2]:

  Ctrl-x Ctrl-o Open a new file in the current buffer.
  Ctrl-x Ctrl-s Save the current file.
  Ctrl-x Ctrl-c Quit.
  
  Ctrl-x c      Create a new buffer
  Ctrl-x n      Move to the next buffer.
  Ctrl-x p      Move to the previous buffer.
  Ctrl-x b      Select buffer from a list
  
  M-x           Evaluate lua at the prompt.
  Ctrl-r:       Regular expression search.

  sudo apt-get install some_package
  sudo yum -y install some_package
  pacman -S some_package
  ...