"Away, you starveling, you elf-skin."
Hanmer and Warburton were right, I think, in reading eel for 'elf.'
"You dried neat's tongue, you bull's pizzle, you stock-fish."
"There is virtue in that Falstaff; him keep with."
The poet probably wrote 'him keep with thee.'
"Misleader of youth, Falstaff, that old, white-bearded Satan."
It would be better, both for emphasis and metre, to read 'that Falstaff.'