I don't understand all the re-melting.
Cosmetics?

What does the 4 ounces of trim weigh after you dry it?

That is where most of the lost butter will be found.
And do not discard the dross.
Put it in a sieve and pour boiling water through it as a rinse.
That will recover some, but not all.
The only way to get the rest of it, and some more resin as well, is to wash it with a solvent like ethanol and then evaporate the solvent.

It is very difficult to quantify an extraction using butter.
If you want maximum efficiency and yield, it's best to extract the resin with a frozen ethanol wash first.
With good bud, that can yield 22% or very pure oil by weight.
Purge the solvent and then just add the proper amount of oil to your butter for the strength desired.

There is an added advantage.
You can do a proper decarboxylation, of the oil in a half hour at around ~250 F. with a coffee warmer.
Saves on energy.

Just my 2 cents.
TIOLI.

Aloha,
Weezard