I would suggest treating the page like a funnel to convert Facebook followers to engaged email subscribers first, then think more about where to direct that engagement after. 

General steps I would follow:

1. Ramp activity back up and determine a growth strategy. Try to understand the existing audience engagement and the baseline growth rate over a month or so of consistent activity (how many people actually see the posts, how does engagement differ by type of content, do the followers care more about humor or EA, does cross-posting to Instagram get any traction, etc).

2. Create a funnel to convert followers to email subscribers. With no financial investment, this means incorporating email sign ups into the normal posts somehow (maybe every post has a link to sign up, or maybe 1 in 4 posts is solely for promoting the email sign up). If there is capacity for even a little financial investment, it will be possible to target the highly engaged followers with more precision using Facebook ads.

3. Create email campaigns to direct attention to worthwhile areas. What these "worthwhile areas" should be is what you're actually asking about in the post. This could be a variety of things, maybe a longer term goal, or rotate through different short term campaigns. But for now, I think it will be more useful to confront this problem if the first two steps are proven solvable first, especially since details here will depend on how the email audience shapes up (age range, interest areas, etc).

Generally, I think pushing specific conversion goals directly from the Facebook page will be a difficult endeavor, like you've seen with the  attempts you mentioned. The email funnel will be more productive if even a small percent of followers eventually become subscribers, and that will allow the Facebook page to be more focused on growth and reach (something it has already succeeded at).

Doing this well would require a serious time commitment. It really depends on how the first couple months of testing go, but I suspect there is significant upside. If interested, I'm happy to discuss more and see if there's any way I can help!

Talk to u/Infinity, I see them on the EA subreddit every now and then. They singlehandedly provide like 90% of the memes on there, and they're pretty good 👍

Repost some of the best (and most generally accessible) stuff from the 50X smaller Dank EA Memes group? Hope that this gets more people interested in EA. https://m.facebook.com/groups/OMfCT/about/

Maybe advertise local EA meetups as well by the same logic.

Alternatively, go in a more political direction and post consequentialist memes about, eg, the FDA's overly cautious drug approval, the high efficacy of EA causes like global health/development aid, etc. Maybe steal memes from r/neoliberal. But if done poorly, this would run the risk of devolving into a highly obnoxious politicized facebook group. (The trolly problem format is already overused to make dumb political arguments that aren't even very consequentialist.)

For that reason, probably try to move away from the actual "trolly problem" format, and towards being a meme group where what's important is that the jokes have a consequentialist mindset.