1. Please go to the Appereance > Widgets then you just need to edit Twitter Widget (Jegtheme) as you need or simply just change the twiiter usename.
2. Please try to use this link https://www.twitter.com/
3. May i know which text that you mean in this case? Can i see the page that you referring to?
4. Actually you can change the color scheme on the customizer style but it will affect on almost element of your site. It seems you will need to add some custom css code to achieve that.
5. Please take a look at our documentation about adding columns right here http://support.jegtheme.com/documentation/create-columns/