POEdit with Custom mu-plugins code

I have a very strict directory structure I must adhere to within mu-plugins, but I would like POEdit to be able to help me generate translation files for specific code within this structure, while ignoring a bunch of others.

At the moment, POEdit is having difficulty locating valid code. I have purchased the Pro version, but I think my structure is too customized to be able to benefit from the automated features of Pro. I have also tried using the blank WordPress .pot file located at https://github.com/fxbenard/Blank-WordPress-Pot as a starting point, but I’m still getting similar results.

Here is my structure:

- mu-plugins
   - vendor [don't translate]
   - languages [.mo, .po and .pot files should go here]
   - client [translate some of these]
      - Custom_Class
         - Custom_Class.php [the file that is automatically loaded by _loader.php]
      - Custom_Class_2
         - Custom_Class_2.php [file that is automatically loaded by _loader.php]
         - includes
             - Included_File_1.php [files included by Custom_Class_2.php]
      - react_app [all these files should be EXCLUDED, especially node_modules/*]
   - _loader.php [contains the WordPress plugin headers, and includes all the other php files within the other folders]

_loader.php has the following:

define( 'MY_TEXTDOMAIN', 'MY_TEXTDOMAIN' );
function load_mu_plugin_textdomain(){
    load_plugin_textdomain( MY_TEXTDOMAIN, false, plugin_dit_path( __FILE__ ) );
}
add_action( 'plugins-loaded', 'load_mu_plugin_textdomain' );

note: there are typos in the above code that are addressed in my answer below. Leaving this here for a record of the problem.

I’m using the define() exclusively for IDE code completion. As you can see, the string is the same as the constant, so POEdit shouldn’t have a problem finding things like __( 'my string', MY_TEXTDOMAIN );

I realize there are a number of non-standard approaches from a POEdit perspective, but I feel I should be able to manually customize my .pot file to handle this. Here’s my .pot file as it stands:

# WordPress Blank Pot
# Copyright (C) 2014 ...
# This file is distributed under the GNU General Public License v2 or later.
msgid ""
msgstr ""
"Project-Id-Version: MY_PROJECT\n"
"POT-Creation-Date: 2012-10-05 10:50+0100\n"
"PO-Revision-Date: \n"
"Last-Translator: Your Name <you@example.com>\n"
"Language-Team: Your Team <translations@example.com>\n"
"Report-Msgid-Bugs-To: Translator Name <translations@example.com>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=2; plural=n != 1;\n"
"X-Textdomain-Support: yes"
"X-Generator: Poedit 1.6.4\n"
"X-Poedit-SourceCharset: UTF-8\n"
"X-Poedit-KeywordsList: __;_e;esc_html_e;esc_html_x:1,2c;esc_html__;esc_attr_e;esc_attr_x:1,2c;esc_attr__;_ex:1,2c;_nx:4c,1,2;_nx_noop:4c,1,2;_x:1,2c;_n:1,2;_n_noop:1,2;__ngettext:1,2;__ngettext_noop:1,2;_c,_nc:4c,1,2;\n"
"X-Poedit-Basepath: ../client/\n"
"X-Poedit-SearchPath-0: .\n"
"X-Poedit-Language: English\n"
"X-Poedit-Country: UNITED STATES\n"
"X-Poedit-Bookmarks: \n"

I’m not 100% sure this is the only issue that was preventing POEdit from correctly parsing my code (I’m not sure it actually cares about the WordPress side of things), but fixing these (stupid) errors and re-running POEdit from the .pot file below seems to have generated the correct translation strings:

define( 'MY_TEXTDOMAIN', 'MY_TEXTDOMAIN' );
function load_mu_plugin_textdomain(){
    load_plugin_textdomain( MY_TEXTDOMAIN, false, plugin_dir_path( __FILE__ ) );
}
add_action( 'muplugins_loaded', 'load_mu_plugin_textdomain' );

Changed from my original post:

muplugins_loaded instead of plugins-loaded (which is not an action anyway: plugins_loaded is the correct action hook – note the underscore instead of the dash).

plugin_dir_path() instead of the typo: plugin_dit_path()

Here’s the updated .pot file that I loaded and then generated a new translation for:

# WordPress Blank Pot
# Copyright (C) 2014 ...
# This file is distributed under the GNU General Public License v2 or later.
msgid ""
msgstr ""
"Project-Id-Version: MY_PROJECT\n"
"POT-Creation-Date: 2012-10-05 10:50+0100\n"
"PO-Revision-Date: \n"
"Last-Translator: Your Name <you@example.com>\n"
"Language-Team: Your Team <translations@example.com>\n"
"Report-Msgid-Bugs-To: Translator Name <translations@example.com>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=2; plural=n != 1;\n"
"X-Textdomain-Support: yes"
"X-Generator: Poedit 1.6.4\n"
"X-Poedit-SourceCharset: UTF-8\n"
"X-Poedit-KeywordsList: __;_e;esc_html_e;esc_html_x:1,2c;esc_html__;esc_attr_e;esc_attr_x:1,2c;esc_attr__;_ex:1,2c;_nx:4c,1,2;_nx_noop:4c,1,2;_x:1,2c;_n:1,2;_n_noop:1,2;__ngettext:1,2;__ngettext_noop:1,2;_c,_nc:4c,1,2;\n"
"X-Poedit-Basepath: ../client/\n"
"X-Poedit-SearchPath-0: .\n"
"X-Poedit-Language: English\n"
"X-Poedit-Country: UNITED STATES\n"
"X-Poedit-Bookmarks: \n"