I agree with Mick that the BN may have been territorial, and that caused the HFL to hide. Now with the BN gone, the HFL feels more comfortable.
Mick also said his young one is out all the time looking for food, and mine are the same. My older ones are hidden and skittish and my young ones are much braver. I would vary the HFL diet a bit. Mine really like quality flake (I like Omega 1), shrimp pellets, blood worms, . . . since my tank is mixed I feed a variety of foods for the different fish, and the HFL eat a bit of all of it. Mine don't eat snails, but they have so many other foods to chose from. Mine like to filter feed and I see stuff filtered out of their gills while they eat.
When you have a chance I would get a couple more HFL because they do like company. Mine lay all over each other.
The HFL wouldn't fight with the Corica, but I bet the Corica might give him a hard time. I had 4, and they were fine for about a year, and then they disappeared one by one. Other people have never had a problem with them. My HFL are very gentle living with the smallest fry and shrimplets without predation.
I think that's really funny about the Betta flaring at the Pimafix bottle.

I can see it.
I know more people than me and Mick have HFL on this forum, so I am sure they will chime in. Sounds like your HFL is just fine.

Do you have pictures? Everyone likes pictures.
I have six BN, and I love them. They are not overly aggressive, but I believe I am a little overstocked, and I think any aggression is spread out, and my tank is much bigger.