Hi,
I reviewed your summary in detail and have the enough experience of developing chat web site and using Firebase DB.
As you know, to make the node projects requires more works than to make WP or CMS projects even if it has good performance.
So I raised my budget or deadline a little.
do you need the admin panel to manage the messages?
If so, I am going to consider the budget.
If you want to get a true clean site and a credible developer, let's work together.
Hope to hear from you.
Best Regards, Vadim