You have made a good start with your ideas and approach – here are a few more to consider:
I am a podcast enthusiast one of the ways in which I choose what to listen to is the good old-fashioned google search for top <> podcasts 2020, so one suggestion I would make would be to consider engaging with publishers who have promoted podcasts previously to see if you can make the list. Particularly now with Auckland at Level 3 and people promoting what to do at home. For example: https://www.viva.co.nz/article/food-drink/food-related-podcasts-to-listen-to/ and https://www.purewow.com/food/food-podcasts and https://www.nzherald.co.nz/entertainment/news/article.cfm?c_id=1501119&objectid=12322172.
Facebook: You mention your reach is limited with the number of followers you have. Consider joining Foodie related fan groups. A quick facebook search of foodies returned a number of results – see if you can join and share the podcast details. Although with a cost, consider paid advertising to reach your desired demographic – link the advertising to the demographic profile (use the interests option and choose food related interests).
guest promotion: you have exceptional guests – ask them to do more. Give them an idea for a competition to offer their social media fans and perhaps tag to the end of the podcast (if you have enjoyed this podcast comment on this platform and go in the draw to win – listen and rate the episode they feature in and go in the draw to win – (cookbook, peanut butter, signed menu, etc). Remind them of the benefit of linking to the episode from their digital assets – the enhanced credibility and reach and access to the audiences of the other guests – a win for all!
Network: I see you are part of a team of podcasters – have you promoted your podcast in the other podcasts? Perhaps run a trailer episode? Think Wondery who promote all of their content across the podcast portfolio.
youtube: Can you film any of the interviews and load content onto youtube as a teaser?
content: look to publish transcripts of the interviews on your website – this will help with SEO.
call to action/audience engagement: i listened to the peanut butter podcast and thought you could have asked at the end for the listener, assuming they enjoyed the episode to tell their friends, like it etc. Perhaps also a bit of a teaser for the show next week? Ask the audience if they want to submit ideas as to who you should interview and why.