Help with using Multiscrape with Form-submit to log into Lose It!

Configuration
5

The following makes sense in the context of this guide.

My configuration.yaml includes:

shell_command:
  browserless_scraper: "bash ./scripts/browserless_scraper.sh {{function}} {{output}}"

multiscrape:
    - name: Scraper McScrapeface
      resource: "http://localhost:8123/local/browserless/my_output.html"
      scan_interval: 0
      timeout: 30
      log_response: true
      method: GET
      sensor:
        - name: Calories Remaining
          unique_id: calories_remaining
          select: "div > table > tbody > tr:nth-child(3) > td > table > tbody > tr > td:nth-child(2) > table > tbody > tr:nth-child(1) > td > table > tbody > tr:nth-child(2) > td > div > div > table > tbody > tr:nth-child(3) > td > table > tbody > tr > td > div"

My browserless_scraper.sh looks like:

#!/bin/sh
curl -X POST 'http://homeassistant.local:3000/function' --data-binary '@/config/js_scrapers/'$1 -H 'Content-Type: application/javascript' > /config/www/browserless/$2

My automation looks like:

alias: When triggered, update Calories remaining
description: ""
triggers: []
conditions: []
actions:
  - data:
      function: my_scraper.js
      output: my_output.html
    action: shell_command.browserless_scraper
    alias: Scrapes HTML into /homeassistant/www/browserless/my_output.html
  - delay:
      hours: 0
      minutes: 0
      seconds: 2
      milliseconds: 0
  - data: {}
    action: multiscrape.trigger_scraper_mcscrapeface
    alias: >-
      Reads my_output.html and updates sensor.calories_left in
      /homeassistant/configuration.yaml
mode: single

My my_scraper.js looks like this (I use http://homeassistant.local:3000/debugger/ for running in-browser debugging):

export default async ({ page }) => {
  await page.goto("https://my.loseit.com/login");
  await page.type('input[id*="email"]', "YOUR EMAIL GOES HERE");
  await page.type(
    'input[id*="password"]',
    "YOUR PASSWORD GOES HERE"
  );

  await Promise.all([
    page.keyboard.press('Enter'),
    page.waitForNavigation(),
  ]);

  await Promise.all([
    page.goto("https://www.loseit.com/#Home"),
    page.waitForSelector("div > table > tbody > tr:nth-child(3) > td > table > tbody > tr > td:nth-child(2) > table > tbody > tr:nth-child(1) > td > table > tbody > tr:nth-child(2) > td > div > div > table > tbody > tr:nth-child(3) > td > table > tbody > tr > td > div"),
  ]);

  const html = await page.content();

  return html;
};