cardano-wallet-js VS browserify

For point 5, I'd look at a project such as this for JavaScript code. Otherwise, you can use the Cardano CLI available on IOHK's GitHub, and just call a child process in Node.js and execute commands that way to do what you need. I haven't looked into this enough to know whether or not the code can run client-side in the browser or if you need to run it server-side. I do agree that providing a random website your private key would be very risky and goes against everything crypto stands for, and if that's the case with Cardano dApps, then we might see a rise in Electron JS apps.

Browserify to use node packages in the browser.

Browserify is a widely used JavaScript bundler with over 2 million NPM weekly downloads. In addition to Node.js support, allowing developers to use require() statements in the browser is one of its highlighted features.

This began to change when NPM came in and running npm install became a quick and easy way to install dependencies. Browserify became the first JavaScript bundler. As its documentation says -

Using Npm Module with Browserify

https://www.npmjs.com/package/browserify probably a little old school, but browserify is probably good enough.

One problem was to run jsDOM as UMD module. But luckly I was able to use browserify to compile jsDOM into UMD.

Browserify

https://browserify.org/ is an easy one to get started with.