Make 3 List called Images, titles and subtitles and add items into it instead of adding it to the YoutubeList. After it finishes Call the Input Function of the Card View and set the images to the images list title to the titles list and subtitles to the subtitles list.
Make sure not to place the CardView Input Block in the loop. Place it after the loop
For your question number 3: Yes but only if it is your channel, otherwise you need a licence for that from the channel owner.This licence you have to show in your policy,term of use to the user. If you dont publish his licence there, you app will be rejected.
I have heard that Google is going to make some amendments in their API system so projects like YouTube sub counter etc can suffer for some time, I don’t know if Google has already done this or going to do this in near future, I will try Adding some accurate info about it tomorrow