I can't help but mention that I rather like the alternative approach of keeping steps 1-3, and using Phoenix LiveView (or C#'s Blazor?) for the rest. Not saying it's better or worse, but I quite like it.
Do you have good resources for learning Elixir with OTP and Phoenix ? I also believe LiveView can deliver the 80% of functionalities for 20% of the price, so I'm very interested in learning it
"Programming Elixir" and "Designing Elixir Systems with OTP" are also good, the former more so if you get started. From what I remember "Programming Phoenix" was enough to get started though, and these two books are better at getting deeper knowledge of Elixir/OTP.