Hello Zaffar, I'm here to pick on one of your methods. The icons that come with multiple models you've uploaded have a filesize of 512kb for HD, and 26kb for SD. This is ridiculous
You can use the settings as shown below to SIGNIFICANTLY decrease the file size.
I've attached an example of this compression as well.
With this, the icons should come out to be around 40kb for HD, and 2.5kb for SD (Assuming SD also uses .dds and not .blp)