[Mashiro]

Fixing the too many HTTP requests issue is actually quite easy.

You have to find all resources that are loaded over a HTTP link and change it to HTTPS. If something is not loading after that the issue might be that the server from where the resource was loaded doesn't support HTTPs. In this case I recommend to host the script yourself on HTTPS or find a mirror with HTTPs. Most script and style CDNs actually all support HTTPs. Just the theme or plugin developers are absolutely lazy and don't bother with putting HTTPS links or simple //domain.extension/filename.extension links that automatically adjust to the protocol used on the parent site.

To find the resources you can either simply check the source code of your page or use the web browser development console. Furthermore maybe that testing site can even tell you what is loaded over HTTP. The issue is absolutely unrelated to whether CDNs should be used to host scripts or not. Only relation to CDN here is as said before if that CDN doesn't support HTTPS. In that case you either look for one that has HTTPs or really host it yourself on your HTTPS server.