There is an exception in the case of a series. If the videos are closely related (similar topics, similar format) they can be considered part of a series. That means 5 tracks for 6 series if they have the same topic and format.
For 2.)
I don´t know
For 3.)
If it´s a part of an existing YT meditation series, you don´t need - I guess.
For Own advertisement: Check out my MEDITATION collection if you like:
Ein weiterer Meditations Track ist zur Zeit in der Queue.
If you consider your podcasts to be part of a same series (shared topic: meditation) then:
Yes you can. The “series policy” allows for up to 52 episodes. Here you would have 6 uses per license, so you’re covered.
Not exactly. Typically Audiojungle licenses do not have time limitation. However the series policy allows the series to run for a year max with a same license. The year limitation does not start on the day you buy but rather on the day of the first episode publishing.
If more than a year goes by before you upload new episodes you would have to buy new licenses for those episodes as they wouldn’t fit the “up to one year” policy.