Hi there,
Welcome to SeaTheme forum.

1. Please set width for desktop and mobile inputs then it will show.

2. Please try to drag&drop the Modules into a Group, you can set alignment on this Group settings, the Modules within the Group will follow the alignment:

3. It is possible to set Background Video with a Group module(check how).

It is possible by a Embed module also, it supports Hosted video, you can use mp4 format video.

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook

Hi,

Please click plus icon on the top bar of BM content builder, you will see Group :

If you edit a new page, you can direct see the Group :

Or you can directly insert a pre-made template of with BG video Group , I recorded a quick video guide here, please click to watch it.

Both Group and Embed support a hosted(uploaded) video and autoplay.
ps: Embed is not only support Youtube/Vimeo, also support hosted video. And please note that the autoplay video must be muted because it is rule of browsers

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook