These are excellent questions, because so much depends on the kind of interest/engagement your respondents have in the choice task. If you're struggling to get engagement, then perhaps you need to give up some precision at the individual level (via a shorter ACBC survey) in favor of not inviting respondents to answer sloppily just to finish the survey.
A lot depends on whether you feel your sample size is ample enough to field a sparser/quicker ACBC survey. For example, if you had 800 respondents, you could feel much better about reducing the information content and reducing the statistical precision at the individual level compared to if you have only 100 respondents.
Regarding the final section, the "purchase likelihood" questions. You only need to ask those if you need to recalibrate the "None" utility to be tied to some threshold point on the 5-pt purchase intent scale. Many (most?) people don't bother with that final section.