it sounds like a huge amount but it's about right.
I used 12 ounces dried in 5 gallons last time. this is a moderately large sackful as you can imagine.
I was not using hops so I used about half at the beginning of the boil and half at flameout.
They are a mess to deal with so either bag them or prepare to filter your wort through something. I like a big BIAB type grain bag inside my bucket. then when you are done running off you can gently and slowly lift the bag out and get all the solids.
It's a delicate flavor and you get less bitterness and more mild tea like astringency from the early additions. it serves to balance the sweetness though so that's nice. The later additions are also very subtle. I have considered dry-tipping but I have read a fair number of reports of infections from dry-tipping so I have not tried it yet. Not that I'm particularly afraid of wild yeasts, in fact historically the microbiology of heather tips was prized for mead making in the celtic lands.