How to create a view displaying fields only from block it was created in (Custom Blocks Types + Paragraphs)
To start, I cannot think of any benefits for creating a block type to act as a container element for slideshows. Especially since you will be using views to create the slideshow. If you like, please write in a comment why you felt it was a good idea. IMO content types make more sense.

The main cause of your problem is probably a misunderstanding of what is happening. A paragraph field on a drupal entity (block, node, whatever) is a one to many relationship. Every paragraph you add to the field will be a separate entity with its own id. If you have a contextual filter on the paragraph id, it does make sense that Drupal only loads one slide. You instruct it to load one id. (In fact I am surprised that you somehow managed to show more). 

Normally you would add the reverse relationship (from paragraph item to container entity) and then use a contextual filter on the container entity: I would create a slideshow of paragraph items, add a relationship to the node and then use a contextual filter on node id. Then if I filter on node id 1, I would see all paragraph items linked to node 1.

Since you are now dealing with a block, I think you might be able to build a similar construction (relationship to the block and contextual filter on block id?) But I encourage you to reconsider.