What a great question and thanks for attaching that print page. It's very helpful. It seems quite clear that italics is used for all the English words, including the actual translation of the entry. We can take that as a cue.
You are absolutely correct that the colon is inserted ONLY after the complete entry, in this case after "acceptus." The italics for the English is ignored and the English is contracted. The colon signals the reader that there is the language shift to English and that the entry is completed and the English translation follows. This is what Section 12 means when it says to ignore typeface in all translations.
But you have English WITHIN the entry and there, follow print. Use italics and contracted English. Italics here will signal the reader of the language shift within this entry so they know that non-italicized words continue to be in Spanish. Note also that Rule 12b (3) just below the directive to ignore typeface, says to RETAIN typeface WITHIN the entry. Such is the case here.
As noted elsewhere in the manual, the shift from one language to another is usually quite apparent visually to the print reader, but much less so to the braille reader. This is the reason for the various braille usages when the two language are in proximity.