No, you need to enable "Who can upload Featured Image" option and upload it manually if you want to make a beautiful slider. The thumbnail was get automatically from youtube, dailymotion, wistia... are bad.
1. You can not. It only shows the popup that you created in ACP.
2. It supports HTML, you can add html code to the popup content.
I'll send you a demo page.
It has qn optiob to select which forums to use Gallery view. The Gallery has masonry layout, it doesn't use equal heights, so you should upload the images that have the same height & width.
I don't use that theme, it may be missing the default class of ipb so the plugin can not find the hook point. Please give me acp access I'll can take a look.