My experience with proxies and facebook precisely:
- I tried apify proxies for anonymous access to fb public data (pages, public profiles, public groups) and faced soft-blocking (response data under IP from proxies either limited or leads to auth, issue confirmed by apify support and they can do nothing about it)
- Popular alternatives like BrightData (ex-luminati) or Soax just too expensive, so skipped them
- Ended up using Proxy6 (dot net) - price was very important since I delivered paid custom solution under apify cloud, customer was not willing to pay high running costs for scraping small chunks of public fb data on demand (hi-res images and hd videos, they offer SaaS to create custom ads based on public fb content, so its relatively low traffic over long time range).
Your case is different since you have auth-based access, imho still worth trying. I used auth based access to scrape bulk fb data (posts from pages), but it was 2 years ago and at that time apify proxies worked for me.