Please don’t attribute too much weight to my comments. I’m making something entirely different and don’t spend time on podcasts, so I don’t know your audience and industry.
I’d suggest dropping to 3 tiers:
$5: thanks in credits, early-release episode schedule (draft of upcoming episodes, not early-access to content), access to transcripts, links, additional details in patron-exclusive posts
$15: as above, plus: special polls to set episode schedule (assist in drafting schedule by polls feature, highest votes get produced first), early access to draft content under revision (snippets, cutting-room floor, sound bites, that sort of thing, not full recordings without edits), something cool from the interviewee, like a signed hat or postcard, a promo code for downloading content elsewhere, etc. (probably a stretch goal for the future to offer collaborations in that way)
$30: as above, plus: periodic drawings to serve as co-host, chance to volunteer for co-production, like assisting editing, meeting interviewees, etc. (probably something worth a bit more than $30 monthly, so maybe keep this behind a 3-month minimum tier membership or more)
Set up public polls to all all audience to place votes for possible future content, then mix it up a bit to create a poll for that middle tier to set the content schedule.
Keep up periodic public content related to a recent episode for all audience to be involved, like the highest voted content might be a free episode, then the other content pieces are behind the tier pledge pay-wall.