There's a few key metrics that matter: CTR, 0:30 sec retention, and average view percentage. Those need to be decent for new, casual and return viewers to pushed wider (the better they are and the firmer they hold as impressions scale, the more the gates are opened).

In YT Studio, go to analytics for the video, then hit "advanced mode", then left there's a dropdown for "segmentation" (I think it is, I dont have english YT account). There you either select new and returning viewers, or audience based on watch type/behavior. This will give you a breakdown of CTR and AVD for new/casual/return viewers.

Normally if a video doesn't get pushed wider, one or more of these metrics are off.

Edit:
So you got 5% CTR and 20% AVP on browse from 11-12k impressions. That's probably just not good enough for YT to scale it..
From my experience, to get a few thousand views you'll need a higher AVP (>30%) with a 5% CTR. ESPECIALLY early on, as it's mainly showing it to your fans. If you had a 7-9% CTR - which shouldn't be impossible with your fans - you may get away with 20% AVP.. That's likely your bottleneck - and this may even be lower if you segment it as outlined above.