"This fierce abridgement
Hath to it circumstantial branches."
For 'fierce,' which yields no good sense, I read first. 'Abridgement' is summary: "This brief abridgement of my will I make" (Lucrece).
"Is this most constant wife [To Post.] who even now."
For 'this' we might read thy, or, as I have done, 'this thy.' Without the stage-direction the place has no sense.
"My peace we will begin."
For 'My' Capell read By; others This.