You will use the grid list widget to loop posts. You will create 2 pages named “item” as grid object and “single” as post model.
You can also add shortcode inline to use dynamic content in html.
I recommend you to try the XD theme, it’s complete theme with information about how to use MWuse stuffs.
Yes you can upload one Muse page only.
You need all scripts and assets exported, you can export scripts and assets from Muse (export as HTML), then zip the folder containing this export.
If you want to include the page in an existing WordPress website (as a landing page) then in “wp-admin -> MWuse” you can check “Exclude index from hierarchy”