Tmux scroll in readonly

You can send literal escape (and newline) with ANSI-C quoting (there's more about that here), e.g. to send escape to 0:0:

tmux send-keys -t 0:0 $'\e'

For your mapping, assuming I understand it correctly, you could do something like this:

map  <F5> :silent !tmux send-keys -t 0:0 $'\e'"python"$'\n'<CR>

Note that the escape will always be sent, so to work around the issue of the shell receiving the escape, you could send an extra newline:

map  <F5> :silent !tmux send-keys -t 0:0 $'\e'$'\n'"python"$'\n'<CR>

I'm not entirely sure I understand the first part of the question:

If you want to scroll faster than one page up at a time, you can add a repeat count to page-up: in copy mode do M-10 PageUp (with emacs key bindings) or 10C-b (with vi key bindings) to scroll up 10 pages at a time. However, I'd rather use the search functionality C-s and C-r for emacs keys and / and ? with vi keys.

To capture the entire history of the pane I would do (needs tmux 2.0 or later):

$ tmux capture-pane -S - -E - # save the history in a paste buffer

In case you have an older version of tmux, give something like -S -400000 as an argument to tmux capture-pane.

You can then paste the history wherever you want with prefix-]. To save the history to a file, do:

$ tmux save-buffer /tmp/myhistory # save the history in /tmp/myhistory

I have the line

bind-key C command-prompt -p 'save history to:' \
         -I '/tmp/tmux-%F_%H_%M.log \
         capture-pane -S -; save-buffer %1'

in my $HOME/.tmux.conf (which I adapted from this answer). This prompts me where I want to save the entire history with a reasonable default.

If you wish to save some memory, delete it using $ tmux delete-buffer.