Would I get a warning from Verizon fios for downloading the Despecialized Editions since the file size is huge? Also can I stream it from my pc to tv via chromecast?
ISPs have absolutely no business dictating how large of files you are allowed to download. That said, for many Comcast jurisdictions, you would be using almost 10% of your monthly cap. As far as I know, Verizon is fully operating in the 21st century when it comes to stuff like caps (i.e., they don’t have them).
Chromecast doesn’t play MKVs and it doesn’t like DTS audio. So you’ll need to convert it to a format that works.