Your first point is the one most service businesses miss. "Website help" sells nothing because the buyer cannot picture what arrives, while "20 researched companies, each fact with a source link" can be judged before any money moves.

I would add one line to the scope email: how the buyer will check it is done. "You'll get X, by Y, not including Z" covers the deliverable, and a sentence such as "each company will have a working source link you can click" gives both sides the same test at handover.

On buyers who insist on a call, I have seen it work to offer a short call only after they reply to the written scope. By then the call is about a real document instead of discovery from zero, and it usually takes ten minutes. Some buyers simply trust a voice more than text, and that is fine as long as the agreement still lives in writing.

How often do written enquiries turn into paid jobs for you so far?