You can spot treat every day for a few days in a roll but then I'd give it a week or so break and maybe next time try spot treating with liquid carbon. I also wouldn't drop lighting below 4 hours.
Is it on all the crypt leaves? I'd personally cut the leaves off and get it out of the tank and off the plant. New leaves will grow back.
Staghorn looks way different than BBA. Staghorn is strands of algae that grow and branch like antlers. BBA is fuzzy. Look at the pic's on this site.... James' Planted Tank - Algae Guide
Here's a link that was posted a few months ago that might interest you... The "One-Two Punch" Whole Tank Algae Treatment
I've never tried this as I'm not big into chemicals but I've even read Tom Barr posting about using AlgaeFix in tanks that have stubborn algae. BUT it won't work on BBA. Also some people have had issues during the first few hours of adding it with fish showing respiratory problems. Some lose fish others have great luck with this product. I'd do some serious reading and research on it. There are several threads about people on TPT forum who have and do use it.
Amano shrimp are your best bet for eating algae.